OF THE DELUSIONS WHICH ARISE IN JUDGING OF THE LIMBS.
A painter who has clumsy hands will paint similar hands in his works, and the same will occur with any limb, unless long study has taught him to avoid it. Therefore, O Painter, look carefully what part is most ill-favoured in your own person and take particular pains to correct it in your studies. For if you are coarse, your figures will seem the same and devoid of charm; and it is the same with any part that may be good or poor in yourself; it will be shown in some degree in your figures.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.