"Pythagoras, an immortal mathematical genius, vegetarian and founder of a high-standing school of philosophy, went to Egypt to learn more about the "secret sciences" of that country. Before he was allowed to enter into the school of the learned, called High Priests at this time, he had to undergo a fast of forty days, under supervision, outside of the city. Believing that this was a test of his willpower and energy, he was told this: 'Forty days' fast is necessary in order that you may grasp what we will teach you.'"

Source: Arnold Ehret in "Physical Fitness Thru a Superior Diet"