A Treatise on Painting/Chapter 9
Chap. XI.—The Difference of Proportion between Children and grown Men.
In men and children I find a great difference between the joints of the one and the other in the length of the bones. A man has the length of two heads from the extremity of one shoulder to the other, the same from the shoulder to the elbow, and from the elbow to the fingers; but the child has only one, because Nature gives the proper size first to the seat of the intellect, and afterwards to the other parts.