日 and 月: Transition from pictographs to hanzi I've read an article discussing transition of pictographs for Sun and Moon to hanzi. It raised following questions, but left them unanswered:


Original pictographs for Sun is a circle with point in the center. What is the meaning of the point?
There were added two horizontal lines (splitting it approximately in thirds) during the transition of Moon pictograph to hanzi. What is the meaning of those two lines?


I've searched through web and I have found some explanations, but they don't seem authoritative enough to me (not to mention doubts I have). For the Sun, the only explanation I've found is that the point means sun spot. As for the Moon, explanation stated that those lines mean cloud covering the Moon.

Could someone give me an explanation or recommend a book covering this problems?
I'm afraid that an explanation in any book is probably just speculation. The two characters in question have probably been around as long as Chinese characters themselves.

This site (chineseetymology.org) is a very useful resource for tracing the history of Chinese characters. In particular, it appears that both 日 and 月 were sometimes also written without the extra line, as one would expect from a pictogram:

http://www.chineseetymology.org/CharacterImages/Oracle/J10000/j15800/j15869.gif
http://www.chineseetymology.org/CharacterImages/Oracle/J10000/j15800/j15887.gif

with line http://www.chineseetymology.org/CharacterImages/Oracle/J10000/j16400/j16449.gif
without line http://www.chineseetymology.org/CharacterImages/Oracle/J10000/j16400/j16459.gif

although 日 without the line is rare. (Check the entries of 日 and 月 for many more pictures. The history of these characters starts at least some 3000 years ago with the oracle bone script found at the bottom of the page.)

As for interpreting these pictures, 新漢和大辞典 writes the following


  月  
  
  象形。三日月を描いたもので、まるくえぐったように、中が欠けていく月。
  Pictogram. A drawing of a crescent moon, waning as though being hollowed out.
  
  日  
  
  象形。太陽の姿を描いたもの。
  Pictogram. A drawing of the shape of the sun.


In particular, no word about the line in 日.