There once was a king who belonged to a highly ascetic religion; its monks were expected, for instance, to sleep on beds of nails. He was very puzzled at the practices of the Buddhists, who did not engage in such asceticisms, and once said to some Buddhist monks, "I know that many monks of my religion, even after much mortification, still cannot vanquish their lusts and desires. How mired in sensuality you Buddhist monks must be!"
But the eldest Buddhist monk replied to the king, "Consider this, O King. If you were to release a man condemned to death from prison and decreed that he would be pardoned, but only if he took a bowl of oil and, walking to the next town and back, spilled not a single drop, and if you set in his way musicians and beautiful dancers and fine feasts, what do you suppose he will answer if you then ask him what he saw and heard along the way?"
But the king did not know, and so made an experiment of it himself, releasing a condemned man from prison, granting him pardon on the condition that he spill not a single drop of oil, and setting musicians, dancers, and feasts in his way. And when the man returned -- he had not spilled a drop -- the king asked him, "What did you see and hear on the way?"
And the man replied, "Truly, I heard nothing and saw only the bowl of oil for the entire trip, because I did not dare allow myself to think of anything else."
