First study the science, and then practice the art which is born of that science.

Nature is full of infinite causes that have never occurred in experience.

Nothing will be left, Nothing in the air, nothing under the earth, nothing in the waters. All will be exterminated.

Make your faces so that they do not all have the same expression, as one sees with most painters, but give them different expression, according to age, complexion, and good or bad character.

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.]

Medicine is the restoration of discordant elements; sickness is the discord of the elements infused into the living body.

Especially learn how to see.