"...What we call prajna essence is none other than the potent and wondrous awareness from which the six sense functions flow forth. It is like a room that encompasses empty space, having six doors open on the sides, without obstructing each other. What we call the mind of sentient beings is none other than that which habitually follows the six sense objects of sight, sound, smell, taste, touch, and thought. It constantly grabs and rejects things it encounters, generating feelings of liking and aversion, grasping and attaching [to things] thought after thought, without interruption.
Prajna essence is analogous to water and the mind of sentient beings to waves. When the ocean of mind is perturbed by the wind of conditions it encounters, waves arise from the water. Apart from the water, the waves have no concrete substance. For one whose great wisdom has shone through in great brightness and openness, he or she would be able to see the unmoving water amidst the thousand convoluted waves, with nothing amiss in both movement and non-movement. If you have not attained this, you are only relying on words that resemble [true wisdom], being profoundly blind to the wisdom essence of wondrous awareness..."
-- Chan Master Zhongfeng Mingben,
http://www.chan1.org/ddp/chanmag/win2004.html#wondrous