Yoga Nidra
“Yoga Nidra, which is derived from the tantras, is a powerful technique in which you learn to relax consciously. For absolute relaxation you must remain aware. This is yoga nidra, the state of dynamic sleep. Yoga nidra is a systematic method of inducing complete physical, mental and emotional relaxation. The term yoga nidra is derived from two Sanskrit words, yoga meaning union or one-pointed awareness, and nidra which means sleep. During the practice of yoga nidra, one appears to be asleep, but the consciousness is functioning at a deeper level of awareness. For this reason, yoga nidra is often referred to as psychic sleep or deep relaxation with inner awareness.
In this threshold state between sleep and wakefulness, contact with the subconscious and unconscious dimensions occurs spontaneously. In yoga nidra, the state of relaxation is reached by turning inwards, away from outer experiences. If the consciousness can be separated from external awareness and from sleep, it becomes very powerful and can be applied in many ways, for example, to develop the memory, increase knowledge and creativity, or transform one’s nature.
In the raja yoga of Patanjali there is a state called pratyahara where the mind and mental awareness are dissociated from the sensory channels. Yoga nidra is one aspect of pratyahara which leads to the higher states of concentration and samadhi.”
from the book of Yoga Nidra by Swami Satyananda Saraswati