"Nature is the source of all true knowledge. She has her own logic, her own laws, she has no effect without cause nor invention without necessity."

"Water is the driving force of all nature."

"The human foot is a masterpiece of engineering and a work of art."

"The function of muscle is to pull and not to push, except in the case of the genitals and the tongue."

"Nature never breaks her own laws."

"A bird is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements."

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."

"The human body is a machine which winds its own springs; it is the living image of perpetual motion."

"The shadows of shadows of shadows of a body will be compounded of all the aforesaid tints intermingled."

"In order to arrive at knowledge of the motions of birds in the air, it is first necessary to acquire knowledge of the winds, which we will prove by the motions of water in itself."

"The rivers are the veins of the earth, and the tides are its breathing."

"The span of a man's outstretched arms is equal to his height."