The motive power is the cause of all life.

In the days of thy youth seek to obtain that which shall compensate the losses of thy old age.

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

Art lives from constraints and dies from freedom.

He who thinks little errs much.

Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature because in her inventions nothing is lacking, and nothing is superfluous.

When you look at a wall spotted with stains...you may discover a resemblance to various landscapes, beautiful with mountains, rivers, rocks, trees. Or again, you may see battles and figures in action, or strange faces and costumes, and an endless variety of objects which you could reduce to complete and well-drawn figures.