The Gateless Gate, by Ekai, called Mu-mon, tr. Nyogen Senzaki and Paul Reps [1934], at sacred-texts.com
A monk asked Nansen: "Is there a teaching no master ever preached before?"
Nansen said: "Yes, there is."
"What is it?" asked the monk.
Nansen replied: "It is not mind, it is not Buddha, it is not things."
Mumon's comment: Old Nansen gave away his treasure-words. He must have been greatly upset.