Tokusan was studying Zen under Ryutan. One night he came to Ryutan
and asked many questions. The teacher said: "The night is getting old.
Why don't you retire?"
So Tokusan bowed and opened the screen to go out, observing: "It is
very dark outside."
Ryutan offered Tokusan a lighted candle to find his way. Just as Tokusan
received it, Ryutan blew it out. At that moment the mind of Tokusan was
opened.