OF THE SELECTION OF BEAUTIFUL FACES.
It seems to me to be no small charm in a painter when he gives his figures a pleasing air, and this grace, if he have it not by nature, he may acquire by incidental study in this way: Look about you and take the best parts of many beautiful faces, of which the beauty is confirmed rather by public fame than by your own judgment; for you might be mistaken and choose faces which have some resemblance to your own. For it would seem that such resemblances often please us; and if you should be ugly, you would select faces that were not beautiful and you would then make ugly faces, as many painters do. For often a master’s work resembles himself. So select beauties as I tell you, and fix them in your mind.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.