I have discovered that a screw-shaped device such as this, if it is well made from starched linen, will rise in the air if turned quickly.
Leonardo da VinciThose who are enamoured of practice without science are like a pilot who goes into a ship without rudder or compass and never has any certainty of where he is going. Practice should always be based upon a sound knowledge of theory.
Leonardo da VinciOysters open completely when the moon is full; and when the crab sees one it throws a piece of stone or seaweed into it and the oyster cannot close again so that it serves the crab for meat. Such is the fate of him who opens his mouth too much and thereby puts himself at the mercy of the listener.
Leonardo da Vinci