Hekiganroku - Case 90: Chimon and the "Prajna Wisdom"

A monk asked Chimon,
  "What is the substance of Prajna Wisdom?"
Chimon said, 
  "The clam swallows the bright moon." [1]
The monk asked,
  "What is the use of Prajna Wisdom?"
Chimon said,
  "A female rabbit becomes pregnant." [2]

[1]: A Chinese metaphor expressing how a pearl is formed.
[2]: According to a Chinese legend, a female rabbit becomes pregnant when it
     swallows the light of the full moon.