What happens when you simply sit? The whole energy that has been moving in the body, outside the body, in actions, is no more moving. You become a pool of energy. The energy goes on gathering; you become a reservoir. In zazen you are not even allowed to sway or move your body, not even a slight movement, so no energy is invested in action; all energy becomes available. It goes on falling inside. It fills you. It starts overflowing. When the moment comes of overflowing, there is satori.
Satori is a moment of energy overflowing. Thinking stops by and by. It takes time – almost three days is the time. If you exert day and night, continuously, somewhere in three days the moment comes when the energy is so much it simply explodes. Everything calms down – a sudden lightning inside. Everything becomes clear – a clarity of perception is achieved. This is what is called satori in Japan.
OSHO: Nirvana the Last Nightmare chp.1