* In Leonardo’s drawing, the relationship between circle and square is determined by the position of the navel, which divides the height of the figure approximately in the proportion of the golden section. It is unlikely, however, that Leonardo actually constructed the circle from the square in this way. In 1490, his mastery of Euclidean geometry would not have been sophisticated enough to do so. Besides, Leonardo’s starting point would have been the body, not a geometrical construction (see Laurenza, “L’uomo geometrico”).