What is the history behind the tradition of making the sign of the cross? Catholics make the sign of the cross by touching the forehead then the chest then lest side then the right then bringing two hands together.

My question What is the history behind the tradition of making the sign of the cross? Why, when, and how did this tradition start?
What is the history behind the tradition of making the sign of the cross?

Throughout the history of the Catholic Church, there have been various ways to make the sign of the cross. Probably one of the best sources would be the Catholic Encyclopedia.


  Sign of the Cross
  
  A term applied to various manual acts, liturgical or devotional in character, which have this at least in common: that by the gesture of tracing two lines intersecting at right angles they indicate symbolically the figure of Christ's cross.
  
  Most commonly and properly the words "sign of the cross" are used of the large cross traced from forehead to breast and from shoulder to shoulder, such as Catholics are taught to make upon themselves when they begin their prayers, and such also as the priest makes at the foot of the altar when he commences Mass with the words: "In nomine Patris et Filii et Spiritus Sancti". (At the beginning of Mass the celebrant makes the sign of the cross by placing his left hand extended under his breast; then raising his right to his forehead, which he touches with the extremities of his fingers, he says: In nomine Patris; then, touching his breast with the same hand, he says: et Filii; touching his left and right shoulders, he says; et Spiritus Sancti; and as he joins his hands again adds: Amen.) The same sign recurs frequently during Mass, e.g. at the words "Adjutorium nostrum in nomine Domini", at the "Indulgentiam" after the Confiteor, etc., as also in the Divine Office, for example at the invocation "Deus in adjutorium nostrum intende", at the beginning of the "Magnificat", the "Benedictus", the "Nunc Dimittis", and on many other occasions.
  
  Another kind of sign of the cross is that made in the air by bishops, priests, and others in blessing persons or material objects. This cross recurs also many times in the liturgy of the Mass and in nearly all the ritual offices connected with the sacraments and sacramentals.
  
  A third variety is represented by the little cross, generally made with the thumb, which the priest or deacon traces for example upon the book of the Gospels and then upon his own forehead, lips, and breast at Mass, as also that made upon the lips in the "Domine labia mea aperies" of the Office, or again upon the forehead of the infant in Baptism, and upon the various organs of sense in Extreme Unction, etc.
  
  Still another variant of the same holy sign may be recognized in the direction of the "Lay Folks Mass Book" (thirteenth century) that the people at the end of the Gospel should trace a cross upon the bench or wall or a book and then kiss it. It was prescribed in some early uses that the priest ascending to the altar before the Introit should first mark a cross upon the altar-cloth and then should kiss the cross so traced. Moreover it would seem that the custom, prevalent in Spain and some other countries, according to which a man, after making the sign of the cross in the ordinary way, apparently kisses his thumb, has a similar origin. The thumb laid across the forefinger forms an image of the cross to which the lips are devoutly pressed.
  
  Of all the above methods of venerating this life-giving symbol and adopting it as an emblem, the marking of a little cross seems to be the most ancient. We have positive evidence in the early Fathers that such a practice was familiar to Christians in the second century. "In all our travels and movements", says Tertullian (De cor. Mil., iii), "in all our coming in and going out, in putting of our shoes, at the bath, at the table, in lighting our candles, in lying down, in sitting down, whatever employment occupieth us, we mark our foreheads with the sign of the cross". On the other hand this must soon have passed into a gesture of benediction, as many quotations from the Fathers in the fourth century would show. Thus St. Cyril of Jerusalem in his "Catecheses" (xiii, 36) remarks: "let us then not be ashamed to confess the Crucified. Be the cross our seal, made with boldness by our fingers on our brow and in every thing; over the bread we eat and the cups we drink, in our comings and in goings; before our sleep, when we lie down and when we awake; when we are travelling, and when we are at rest".
  
  The course of development seems to have been the following. The cross was originally traced by Christians with the thumb or finger on their own foreheads. This practice is attested by numberless allusions in Patristic literature, and it was clearly associated in idea with certain references in Scripture, notably Ezekiel 9:4 (of the mark of the letter Tau); Exodus 17:9-14; and especially Apocalypse 7:3, 9:4 and 14:1. Hardly less early in date is the custom of marking a cross on objects — already Tertullian speaks of the Christian woman "signing" her bed (cum lectulum tuum signas, "Ad uxor.", ii, 5) before retiring to rest—and we soon hear also of the sign of the cross being traced on the lips (Jerome, "Epitaph. Paulæ") and on the heart (Prudentius, "Cathem.", vi, 129). Not unnaturally if the object were more remote, the cross which was directed towards it had to be made in the air. Thus Epiphanius tells us (Adv. Hær., xxx, 12) of a certain holy man Josephus, who imparted to a vessel of water the power of overthrowing magical incantations by "making over the vessel with his finger the seal of the cross" pronouncing the while a form of prayer. Again half a century later Sozomen, the church historian (VII, xxvi), describes how Bishop Donatus when attacked by a dragon "made the sign of the cross with his finger in the air and spat upon the monster". All this obviously leads up to the suggestion of a larger cross made over the whole body, and perhaps the earliest example which can be quoted comes to us from a Georgian source, possibly of the fourth or fifth century. In the life of St. Nino, a woman saint, honoured as the Apostle of Georgia, we are told in these terms of a miracle worked by her: "St. Nino began to pray and entreat God for a long time. Then she took her (wooden) cross and with it touched the Queen's head, her feet and her shoulders, making the sign of the cross and straightway she was cured" (Studia Biblica, V, 32).
  
  It appears on the whole probable that the general introduction of our present larger cross (from brow to breast and from shoulder to shoulder) was an indirect result of the Monophysite controversy. The use of the thumb alone or the single forefinger, which so long as only a small cross was traced upon the forehead was almost inevitable, seems to have given way for symbolic reasons to the use of two fingers (the forefinger and middle finger, or thumb and forefinger) as typifying the two natures and two wills in Jesus Christ. But if two fingers were to be employed, the large cross, in which forehead, breast, etc. were merely touched, suggested itself as the only natural gesture. Indeed some large movement of the sort was required to make it perceptible that a man was using two fingers rather than one. At a somewhat later date, throughout the greater part of the East, three fingers, or rather the thumb and two fingers were displayed, while the ring and little finger were folded back upon the palm. These two were held to symbolize the two natures or wills in Christ, while the extended three denoted the three Persons of the Blessed Trinity. At the same time these fingers were so held as to indicate the common abbreviation I X C (Iesous Christos Soter), the forefinger representing the I, the middle finger crossed with the thumb standing for the X and the bent middle finger serving to suggest the C. In Armenia, however, the sign of the cross made with two fingers is still retained to the present day. Much of this symbolism passed to the West, though at a later date.
  
  On the whole it seems probable that the ultimate prevalence of the larger cross is due to an instruction of Leo IV in the middle of the ninth century. "Sign the chalice and the host", he wrote, "with a right cross and not with circles or with a varying of the fingers, but with two fingers stretched out and the thumb hidden within them, by which the Trinity is symbolized. Take heed to make this sign rightly, for otherwise you can bless nothing" (see Georgi, "Liturg. Rom. Pont.", III, 37). Although this, of course, primarily applies to the position of the hand in blessing with the sign of the cross; it seems to have been adapted popularly to the making of the sign of the cross upon oneself. Aelfric (about 1000) probably had it in mind when he tells his hearers in one of his sermons: "A man may wave about wonderfully with his hands without creating any blessing unless he make the sign of the cross. But if he do the fiend will soon be frightened on account of the victorious token. With three fingers one must bless himself for the Holy Trinity" (Thorpe, "The Homilies of the Anglo-Saxon Church" I, 462). Fifty years earlier than this Anglo-Saxon Christians were exhorted to "bless all their bodies seven times with Christ's rood token" (Blicking Hom., 47), which seems to assume this large cross. Bede in his letter to Bishop Egbert advises him to remind his flock "with what frequent diligence to employ upon themselves the sign of our Lord's cross", though here we can draw no inferences as to the kind of cross made. On the other hand when we meet in the so-called "Prayer Book of King Henry" (eleventh century) a direction in the morning prayers to mark with the holy Cross "the four sides of the body", there is a good reason to suppose that the large sign with which we are now familiar is meant.
  
  At this period the manner of making it in the West seems to have been identical with that followed at present in the East, i.e. only three fingers were used, and the hand traveled from the right shoulder to the left. The point, it must be confessed, is not entirely clear and Thalhofer (Liturgik, I, 633) inclines to the opinion that in the passages of Belethus (xxxix), Sicardus (III, iv), Innocent III (De myst. Alt., II, xlvi), and Durandus (V, ii, 13), which are usually appealed to in proof of this, these authors have in mind the small cross made upon the forehead or external objects, in which the hand moves naturally from right to left, and not the big cross made from shoulder to shoulder. Still, a rubric in a manuscript copy of the York Missal clearly requires the priest when signing himself with the paten to touch the left shoulder after the right. Moreover it is at least clear from many pictures and sculptures that in the twelfth and thirteenth centuries the Greek practice of extending only three fingers was adhered to by many Latin Christians. Thus the compiler of the Ancren Riwle (about 1200) directs his nuns at "Deus in adjutorium" to make a little cross from above the forehead down to the breast with three fingers". However there can be little doubt that long before the close of the Middle Ages the large sign of the cross was more commonly made in the West with the open hand and that the bar of the cross was traced from left to right. In the "Myroure of our Ladye" (p. 80) the Bridgettine Nuns of Sion have a mystical reason given to them for the practice: "And then ye bless you with the sygne of the holy crosse, to chase away the fiend with all his deceytes. For, as Chrysostome sayth, wherever the fiends see the signe of the crosse, they flye away, dreading it as a staffe that they are beaten withall. And in thys blessinge ye beginne with youre hande at the hedde downwarde, and then to the lefte side and byleve that our Lord Jesu Christe came down from the head, that is from the Father into erthe by his holy Incarnation, and from the erthe into the left syde, that is hell, by his bitter Passion, and from thence into his Father's righte syde by his glorious Ascension".
  
  The manual act of tracing the cross with the hand or the thumb has at all periods been quite commonly, though not indispensably, accompanied by a form of words. The formula, however, has varied greatly. In the earlier ages we have evidence for such invocation as "The sign of Christ", "The seal of the living God", "In the name of Jesus"; etc. Later we meet "In the name of Jesus of Nazareth", "In the name of the Holy Trinity", "In the name of the Father and of the Son and of the Holy Ghost", "Our help is in the name of the Lord", "O God come to my assistance". Members of the Orthodox Greek Church when blessing themselves with three fingers, as above explained, commonly use the invocation: "Holy God, Holy strong One, Holy Immortal One, Have mercy on us", which words, as is well known, have been retained in their Greek form by the Western Church in the Office for Good Friday.
  
  It is unnecessary to insist upon the effects of grace and power attributed by the Church at all times to the use of the holy sign of the cross. From the earliest period it has been employed in all exorcisms and conjurations as a weapon against the spirits of darkness, and it takes its place not less consistently in the ritual of the sacraments and in every form of blessing and consecration. A famous difficulty is that suggested by the making of the sign of the cross repeatedly over the Host and Chalice after the words of institution have been spoken in the Mass. The true explanation is probably to be found in the fact that at the time these crosses were introduced (they vary too much in the early copies of the Canon to be of primitive institution), the clergy and faithful did not clearly ask themselves at what precise moment the transubstantiation of the elements was effected. They were satisfied to believe that it was the result of the whole of the consecratory prayer which we call the Canon, without determining the exact words which were operative; just as we are now content to know that the Precious Blood is consecrated by the whole word spoken over the chalice, without pausing to reflect whether all the words are necessary. Hence the signs of the cross continue till the end of the Canon and they may be regarded as mentally referred back to a consecration which is still conceived of as incomplete. The process is the reverse of that by which in the Greek Church at the "Great Entrance" the highest marks of honour are paid to the simple elements of bread and wine in anticipation of the consecration which they are to receive shortly afterwards.