O Time! consumer of all things; O envious age! thou dost destroy all things and devour all things with the relentless teeth of years, little by little in a slow death. Helen, when she looked in her mirror, seeing the withered wrinkles made in her face by old age, wept and wondered why she had twice been carried away.

The truth of things is the chief nutriment of superior intellects.

Therefore, O students, study mathematics and do not build without foundations.

The men of experiment are like the ant; they only collect and use. But the bee...gathers its materials from the flowers of the garden and of the field, but transforms and digests it by a power of its own.

Black is like a broken vessel, which is deprived of the capacity to contain anything.

The eye which turns from a white object in the light of the sun and goes into a less fully lighted place will see everything as dark.

The first object of the painter is to make a flat plane appear as a body in relief and projecting from that plane