Never make heads straight on the shoulders, but turn them aside to the right or to the left, even though they look down, or upward, or straight ahead, because it is necessary for them to look lively and awake and not asleep. And do not depict the front or rear half of the whole person so that too much straightness is displaced, one half above or below the other half; and if you should wish to use stiff figures, do so only in portraying old people.

Darkness is absence of light. Shadow is diminution of light.

The wisest and noblest teacher is nature itself.

Truly man is the king of beasts, for his brutality exceeds them. We live by the death of others. We are burial places.

If you do not rest on the good foundation of nature, you will labour with little honor and less profit.

If a man has a tent made of linen of which the apertures have all been stopped up, and be it twelve bracchia across (over twenty-five feet) and twelve in depth, he will be able to throw himself down from any height without sustaining injury. [His concept of the parachute.]

Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.