The Gateless Gate, by Ekai, called Mu-mon, tr. Nyogen Senzaki and Paul Reps [1934], at sacred-texts.com

9. A Buddha before History

A monk asked Seijo: "I understand that a Buddha who lived before recorded history sat in meditation for ten cycles of existence and could not realize the highest truth, and so could not become fully emancipated. Why was this so?"

Seijo replied: "Your question is self-explanatory."

The monk asked: "Since the Buddha was meditating, why could he not fulfill Buddhahood?"

Seijo said: "He was not a Buddha."

Mumon's comment: I will allow his realization, but I will not admit his understanding. When one ignorant attains realization he is a saint. When a saint begins to understand he is ignorant.