In whatever system where the weight attached to the wheel should be the cause of motion of the wheel, without any doubt the center of the gravity of the weight will stop beneath the center of its axle. No instrument devised by human ingenuity, which turns with its wheel, can remedy this effect. Oh, speculators about perpetual motion, how many vain chimeras have you created in the like quest. Go and take you place with the seekers after gold.

Now do you not see that the eye embraces the beauty of the whole world? It counsels and corrects all the arts of mankind... it is the prince of mathematics, and the sciences founded on it are absolutely certain. It has measured the distances and sizes of the stars it has discovered the elements and their location... it has given birth to architecture and to perspective and to the divine art of painting.

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

All our knowledge is the offspring of our perceptions.

For those colours which you wish to be beautiful, always first prepare a pure white ground.

A clever man without wisdom is like a beautiful flower without fragrance.

O Lord, thou givest us everything, at the price of an effort.