From Peter Cohen, answering a question at Quora:
A tea ceremony master was walking through the town market one day when he accidentally jostled a samurai. The samurai took great offense, but because the samurai and the tea ceremony master were of the same social caste, the samurai could not simply lop off the tea ceremony master’s head. So the samurai challenged the tea ceremony master to a duel the following dawn.
Now the tea ceremony master knew nothing of sword fighting, but was bound by honor to show up for this duel. Not wanting to embarrass himself, he went to the town sword master and asked the sword master if he could be taught to use a sword. The sword master was rather flustered, not really being able to teach much in the space of one evening. He showed how to hold a sword, how to do a basic sword stroke, and then said;
“I can teach you nothing about how to fight this evening, but I will tell you this; Go to the bridge in the morning, hold the sword thusly over your head. Think of the tea ceremony. When your opponent approaches, strike with all your might.”
The next morning at dawn the tea ceremony master stood at one end of a bridge and the samurai arrived at the other. The tea ceremony master held up his sword as he had been shown and thought of the tea ceremony. The samurai watched the tea ceremony master for a good while. Finally he bowed, turned, and walked away.