I think it is no small attraction in a painter to be able to give a pleasing air to his figures, and whoever is not naturally possessed of this grace may acquire it by study, as opportunity offers in the following manner: be on the watch to take good parts of many beautiful faces of which the beautiful parts are established by general repute rather than by your own judgement, for you may deceive yourself by selecting faces that resemble your own, since it often seems that such similarities please us; ... so therefore choose the beautiful ones as I tell you and fix them in your mind.
Leonardo da VinciIf you are on the side whence the wind is blowing you will see the trees looking much lighter than you would see them on the other sides; and this is due to the fact that the wind turns up the reverse side of the leaves which in all trees is much whiter than the upper side.
Leonardo da VinciTest knowledge through experience, be prepared to make mistakes, and be persistent about it.
Leonardo da VinciStudy me, reader, if you delight in me, because on very few occasions shall I return to the world, and because the patience for this profession is found in very few, and only in those who wish to compose things anew. Come, oh men, to see the miracles that such studies will disclose to nature.
Leonardo da Vinci