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

Mechanics is the paradise of the mathematical sciences because by means of it one comes to the fruits of mathematics.

It is easier to contend with evil at the first than at the last.

He who wishes to be rich in a day will be hanged in a year.

The first of all simple colours is White ... We shall set down White for the representative of light, without which no colour can be seen; Yellow for the earth; Green for water; Blue for air; Red for fire; and Black for total darkness.

The Book of the science of Mechanics must precede the Book of useful inventions.

Although human ingenuity may devise various inventions which, by the help of various instruments, answer to one and the same purpose, yet will it never discover any inventions more beautiful, more simple or more practical than those of nature, because in her inventions there is nothing lacking and nothing superfluous; and she makes use of no counterpoise when she constructs the limbs of animals in such a way as to correspond to the motion of their bodies, but she puts into them the soul of the body.