The light and heat of the universe comes from the sun, and its cold and darkness from the withdrawal of the sun.
Leonardo da VinciI 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 VinciBut to me all sciences seem vain and full of error that are not born of experience, mother of all certainty, and do not terminate in an actual experience.
Leonardo da Vinci