What story does the King of Salem tell Santiago?

The story is of a boy whose father sends him to learn the secret of happiness from a wise man. The boy discovers a castle where a man gives him a teaspoon with two drops of oil and instructs him to explore the castle for two hours without losing a drop. The boy returns with a full spoon, but has seen nothing. The man sends the boy again and tells him to notice what is around him. When the boy returns again, he has lost the drops of oil, but seen a great deal! The wise man then explains that the secret to happiness is to "see all the marvels of the world, and never forget the drops of oil in the spoon".