Leonardo da Vinci: Drawing of Ideal Proportions of the Human Figure.

This well known drawing by Leonardo da Vinci, about 1500, relates to the only architectural treatise at all, to survive from Antiquity, by Vitruvus Pollio. Although it is unillustrated, it profoundly influenced art throughout history, especially in the period Renaissance.

Vitruv, in the first century b.c., reports the classical ideal of beauty as derived from symmetry and a modular relationship, of the parts to the whole on a mathematical basis. (The smaller part compares to the larger as this to the whole: this is called "The Golden Section" or the "Golden Mean".)

(AB cut at C, so that CB:AC = AC:AB; about 8:13).