Chung-i Hung-en, a disciple of Ma-tsu, was once asked by Yang-shan: "How can one see into one's self-nature?" 
Chung-i said: "it is like a cage with six windows, and there is in it a monkey. When someone calls at the east window, 'Oh monkey, oh monkey!', he answers. At the other window the same answer is obtained. " 
Yang-shan thanked him for the instruction and said: "Your instructive simile is quite intelligible, but there is one thing on which I wish to be enlightened. If inside the monkey is asleep, tired out, what happens when the outside one comes to interview it?" 
Chung-i got down from his straw seat and taking Yan-shan's hand began to dance, saying: "Oh monkey, oh monkey, my interview with you is finished. It is like an animalcule making its nest amoung the eyebrows of a mosquito: it comes out at the street crossing and makes a loud cry: 'Wide is the land, few are the people, and one rarely meets friends!'