The skillful hand and eye must meet the demands placed on them, especially concerning the thicknesses; on which more than one observation can be made. This means that one must give a large number of measurements and outlines relating to thicknesses, in infinite places, for all the limbs and parts, from the fattest body to the leanest and most extended. There should not be fewer outlines and measurements, for every movement and twist of the body and its limbs, or (when one remains still) with the slightest change of position of the viewer. In each case, different outlines and elevations or swellings of the flesh, and also varying degrees of prominence of the bones, will appear, which is generally known. I will only call to help some tangible evidence to illustrate this; such as the head, the leg by the ankle, the arm hanging close to the body, near the hand—all seen narrower from the front than in profile, while the trunk is broader from the front than in profile. Therefore, I conclude confidently that outlines, elevations, and swellings never stand still and cannot, for this reason, be reduced to a rule.

To better accustom myself to the way I have proposed; and to lead my students along this path:

The artist's eye must act according to the demands of the cases. Similarly, concerning sizes on which more than one observation can be made, knowing that one would be obliged to give a great number of measurements and outlines on the subject of thicknesses, in an endless number of places, for all the limbs and parts, from the fattest to the leanest and most extended body; and there should not be a lesser sequence of outlines and dimensions for each movement and turn of the body, and even of limbs as well, or even (if a person makes no movement) at the slightest change of the viewer's position; since, in each case, different outlines and elevations or swelling of the flesh may appear, sometimes also more or less prominence of the bones; which is so generally known that I only need a few concrete proofs to demonstrate it; such as the head, the foot near the ankle, the arm hanging down the side of the body close to the hand, all seen narrower from the front than in profile; the trunk on the contrary being broader from the front; from which I conclude boldly that the outlines, elevations, and swellings never stop; and for this reason cannot be reduced to rule.

To become more familiar with the path I set for myself to follow, and to lead my students there, I have decided: