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

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

"Learning never exhausts the mind."

"Why does the eye see a thing more clearly in dreams than the imagination when awake?"

"Common Sense is that which judges the things given to it by other senses."

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

"Life well spent is long."

"For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return."

"Our life is made by the death of others."

"Life is pretty simple: You do some stuff. Most fails. Some works. You do more of what works. If it works big, others quickly copy it. Then you do something else. The trick is the doing something else."

"It had long since come to my attention that people of accomplishment rarely sat back and let things happen to them. They went out and happened to things."

"Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason."

"He who is fixed to a star does not change his mind."

"Nothing strengthens authority so much as silence."

"As every divided kingdom falls, so every mind divided between many studies confounds and saps itself."

"I love those who can smile in trouble, who can gather strength from distress, and grow brave by reflection. 'Tis the business of little minds to shrink, but they whose heart is firm, and whose conscience approves their conduct, will pursue their principles unto death."

"It's easier to resist at the beginning than at the end."

"Men of lofty genius when they are doing the least work are most active."

"You do ill if you praise, but worse if you censure, what you do not understand."

"Art is never finished, only abandoned."

"I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do."

"The noblest pleasure is the joy of understanding."

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

"Beyond a doubt truth bears the same relation to falsehood as light to darkness."

"Marriage is like putting your hand into a bag of snakes in the hope of pulling out an eel."

"Simplicity is the ultimate sophistication."

"Nature never breaks her own laws."

"Who sows virtue reaps honor."

"Blinding ignorance does mislead us. O! Wretched mortals, open your eyes!"

"A well-spent day brings happy sleep."

"Time stays long enough for anyone who will use it."

"Just as courage imperils life, fear protects it."

"While I thought that I was learning how to live, I have been learning how to die."

"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."

"Experience does not err. Only your judgments err by expecting from her what is not in her power."

"Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory."

"He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast."

"All our knowledge has its origins in our perceptions."

"Where there is shouting, there is no true knowledge."

"I have offended God and mankind because my work didn't reach the quality it should have."

"As a well-spent day brings happy sleep, so a life well spent brings happy death."

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

"The greatest deception men suffer is from their own opinions."

"In rivers, the water that you touch is the last of what has passed and the first of that which comes; so with present time."

"Where the spirit does not work with the hand, there is no art."

"Water is the driving force of all nature."