When and where did Pope Paul VI say the "Mass is the most perfect form of prayer"? I was trying to source this quote, 


  The Mass is the most perfect form of prayer - Pope Paul VI


but the Google, in her wisdom, seems to think I only want to see what my fellow zealous Mary lovers have to write in their circa '96 tabular/framed web pages. 

Usually when someone attributes something to a Pope, they say, "at such and such an audience on the feast of St. So and So" but not this quote, it's just left out there.

What I really want to know is, if the Catholic Church considers Mass to be a Prayer.  I've always heard, and taught, that Mass is the greatest prayer and the Rosary somehow eeks out Eucharistic Adoration and Benediction for the #2 spot (although that logic is troublesome). 

I can't find this tidbit in the Catechism, and my personal collection of wonderful Catholic texts are somewhat older that Pope Paul VI, so please, if anyone has his breviary wherein he scrawled this magnificent truth, please let me know!
James T has identified that the sentiment expressed is Thomist.

I can't find anything positively identifying Paul VI either, but I did find something of Benedict XVI:


  The Eucharistic Celebration is the greatest and highest act of prayer, and constitutes the centre and the source from which even the other forms receive "nourishment": the Liturgy of the Hours, Eucharistic adoration, Lectio divina, the Holy Rosary, meditation. All these expressions of prayer, which have their centre in the Eucharist, fulfil the words of Jesus in the priest's day and in all his life: "I am the good shepherd; I know my own and my own know me, as the Father knows me and I know the Father; and I lay down my life for the sheep" (Jn 10: 14-15).


[However, see also CCC 2763; I'd be interested to know how that apparent contradiction is resolved.]