The navel is the center of the circle, but what do we know about the circle? [br][list][*]The vertical diameter is known, with the center on it.[/*][*]A known point on this vertical diameter is the tangent point at the back of the heel.[/*][*]A 2nd point on the circle is the point where the outstretched arm touches the square.[br]You can define this point out of the given proportions by da Vinci:[br]- The upperside of the chest is at 1/6 of the top of the head.[br]- You can divide this line into 8 parts, with the armpit at 3/8 from the side of the square.[br]- With the armpit as center you can draw a circle through the fingertips. Then the intersection of the circle with the square is a 2nd point on the circle.[/*][*]Two points on the circle define a chord and the perpendicular bisector of a chord runs through the center of the circle.[br][/*][*]So the navel is the intersection of the vertical diameter and the perpendicular bisector of the chord.[/*][/list]Select the checkbox and drag the slider to explore the construction.

Da Vinci provides us all the information to examine how the man fits in the circle as well in the square.[br]A simple construction is enough to confirm that the navel is the center of the circle. Using the written information it should be possible to calculate the exact position of the navel in the square. This is what we'll do in the next activity.[br]The ratio of the naval en the length of the man wasn't an issue for da Vinci. The mastery of the drawing is that da Vinci was the first to combine two drawings in one: the square man and the circular man. In this the navel was just his compass point., not the keypoint for all proportions.