Nan-in, a Japanese master during the Meiji era (1868-1912), received a university professor who came to inquire about Zen.
Nan-in served tea. He poured his visitor's cup full, and then kept on pouring.
The professor watched the overflow...
Mumon's Comment 無門曰、
Nansen, growing old, had no shame. 纔開臭口、家醜外揚。
Just opening his stinking mouth, he let slip the family secrets. 然雖如是、知恩者少。
Yet there are very few who are grateful for his kindness.
The sky clears, the sun shines bright,
The rain comes, the earth gets wet.
He opens his heart and expounds the whole secret,
But I fear he is little appreciated.