There are three classes of people: those who see, those who see when they are shown, those who do not see.

To speak well of a base man is much the same as speaking ill of a good man.

The supreme misfortune is when theory outstrips performance

To speak of this subject you must... explain the nature of the resistance of the air, in the second the anatomy of the bird and its wings, in the third the method of working the wings in their various movements, in the fourth the power of the wings and the tail when the wings are not being moved and when the wind is favourable to serve as guide in various movements.

once you have tasted the taste of sky, you will forever look up

Movement will fail sooner than usefulness.

After painting comes Sculpture, a very noble art, but one that does not in the execution require the same supreme ingenuity as the art of painting, since in two most important and difficult particulars, in foreshortening and in light and shade, for which the painter has to invent a process, sculpture is helped by nature. Moreover, Sculpture does not imitate color which the painter takes pains to attune so that the shadows accompany the lights.