Tzeruf (Kabbalah)

Meditation on the Hebrew letters, their attributes and numerical values would bring the meditator into higher planes of consciousness. Meditation normally began at midnight, with the writing of the sacred letters, seeing the tree of life in the mind's eye and carrying out of breathing exercises. This was a rapid way of achieving [shefa]

(divine influx), but had its perils in that lack of preparation or attempting to achieve too much lead to destruction.