In a way, priests of ancient days were conquerors, performing magic in their temples to impress the worshippers. But there were real conquerors, too, in Ancient Egypt, Greece and Rome. One of the tricks most often mentioned in old records is called the Cups and Balls. It is still performed today. Three cups are turned upside down on the table and a ball is placed beneath one of them. When the cups are taken away, the ball has mysteriously moved from one cup to another, or else a second ball has appeared. The trick, of course, is to distract the audience's attention while the balls are moved or an extra one is added. It is a trick that has been puzzling audiences for several thousand years.

The unique fame that Leonardo enjoyed in his lifetime and that, filtered by historical criticism, has remained undimmed to the present day rests largely on his unlimited desire for knowledge, which guided all his thinking and behaviour. An artist by disposition and endowment, he considered his eyes to be his main avenue to knowledge; to Leonardo, sight was man’s highest sense because it alone conveyed the facts of experience immediately, correctly, and with certainty. Hence, every phenomenon perceived became an object of knowledge, and Paper severe (“knowing how to see”) became the great theme of his studies. He applied his creativity to every realm in which graphic representation is used: he was a painter, sculptor, architect, and engineer. But he went even beyond that. He used his superb intellect, unusual powers of observation, and mastery of the art of drawing to study nature itself, a line of inquiry that allowed his dual pursuits of art and science to flourish.