The practice of Yoga Nidra was developed by Swami Satyananda and turned into a powerful  tool  for relaxation and transformation. The technique is complex, the only proper training is given by the Bihar School of Yoga. 

Yoga Nidra is a relaxation technique derived by Swami Satyananda from an ancient Tantric practice called nyasa (meaning ‘to place’). In the practice of nyasa, specific mantras are ‘placed’ in different parts of the body thus charging them with the energy of the mantras. This is done in a precise order, following a particular body rotation. This traditional practice was adapted for the use of the modern man. Swami Satyananda retained the principle of rotation of consciousness but omitted the mantras in order to enable people from different traditions to practice Yoga Nidra. Yoga Nidra is now a scientific method rather than a religious ritual, but it retains a strong spiritual element.  Yoga Nidra means ‘Yogic sleep’, or ‘psychic sleep’, i.e. sleep with full awareness. To achieve the state of psychic sleep and to be brought back from it the practitioner is led through eight stages. Only four of them are essential. 

The preparation and relaxation stage is essential. It induces the initial relaxation of the body and the mind. The practitioner settles down in savasana with eyes closed, and limbs positioned so that touch sensations are minimized.  The mind is then directed to external sounds, and asked to move through them maintaining a witness-attitude. 

During the second stage, the practitioner makes a resolve, Sankalpa, which is repeated three times. 

The third stage, rotation of consciousness through the body, is essential. The rotation is systematic and follows a definite sequence through 76 parts of the body. This sequence must not be changed. The purpose of rotating awareness through the different parts of the body is to enable the body to be transcended.

The fourth stage is breath awareness and is essential. The awareness is directed to the natural breath. No attempt is made at changing the flow of the breath. One can watch the flow of breath in the nostrils, in the chest, the abdomen, or in a psychic passage between the navel and the throat, and simultaneously count the breaths. 

Experiencing opposite feelings and sensations. Physical and emotional sensations are evoked and intensified in pairs of opposites, and then they are removed. For example, heat/cold sensations, heaviness/lightness, pain/pleasure, love/hate, light/darkness. The purpose is to ‘trick’ the brain to stop registering sensory stimuli as important. This leaves the consciousness free from the normal distractive influx of physical sensations. 

During the sixth stage, visualization, the awareness is directed to the Chidakasha: the psychic space behind the forehead. On this ‘screen’ certain objects, images, symbols, movements, sometimes even short narratives are visualized.  This is the stage when dreaming is induced, but the dreams are controlled and are experienced consciously. The visualization images should be chosen very carefully. Their purpose is to remove tensions from the mind of the practitioner by stirring up old memories and experiencing them with an attitude of a witness. This assists a process of elimination of suppressed feelings and memories and purifies the mind. On a deeper level, the visualization stimulates the subconscious and unconscious levels of the mind. 

Seventh stage involves the repetition of the sankalpa. At this stage of Yoga Nidra, the subconscious mind is deemed most receptive and ready to receive the seed of the resolve. 

Externalization is essential. It is done gradually until the mind returns to waking state. The teacher must give a definite statement that the practice is finished. This should happen before the practitioner moves his body or opens his eyes. This is a safety measure designed to prevent confusing inner with outer perception. 

Yoga Nidra is essentially a pratyahara practice. Pratyahara is the fifth step of raja yoga. It means withdrawal of the consciousness from physical objects. Yoga Nidra induces a state of pratyahara in which perceptions of the outside world in the form of taste, smell, hearing, seeing, touch sensations are stopped. Each stage of the practice causes further withdrawal from the physical objects and the awareness moves inwards. 

During the preparation stage the sight is withdrawn from its objects of perception, the touch sensations are minimized and the hearing is eventually narrowed to the voice of the instructor. This is an initial stage of pratyahara. Deeper introspection is reached through the rotation of awareness, which withdraws the perception from the outside world. Swami Satyananda says that if one is aware of the different parts of the body, then “one will also cease to smell or to taste”. Sense impressions from the instructor’s voice and the mental touch sensations are kept. During the breath awareness stage and the visualization, the instructor’s voice is the only one link with the outside world. If the teacher stops speaking, this link will be removed. Swami Satyananda points that if the teacher chooses the right time to stop speaking, the practitioner will be suspended in a state of pratyahara. 

Depending on the level of spiritual development of the practitioners, Yoga Nidra would bring different benefits which not only are numerous, but also extend far beyond the realm of the body and mind. Most commonly, Yoga Nidra minimizes tension and relaxes the mind, improves physical and mental health, trains the mind and has the power to restructure the personality through the sankalpa and the purification of the subconscious. It works successfully on psychological disorders and psychosomatic diseases such as asthma, insomnia, irritable colon syndrome, high blood pressure. It has an awakening effect on the creativity, improves the memory and increases the learning capacity. Yoga Nidra is also a good educational tool and has provided the basis for innovative techniques such as effortless learning.