Yoga Nidra derives from the tantras and is a powerful technique that Swami Satyananda Saraswati has developed to make it accessible for humanity.

Yoga Nidra is a systemic method of inducing complete physical, mental and emotional relaxation.

In yoga Nidra the state of relaxation is obtained by turning inwards, away from outer experiences.
The practitioner appears to be asleep during yoga Nidra, but the consciousness functions at a deeper level of awareness while dissociating from the sensory channels.
For this reason, many texts describe yoga Nidra as psychic sleep or deep relaxation with inner awareness

In the practice of yoga Nidra, the mind gradually becomes one-pointed while we disengage the other senses. The practitioner only maintains awareness of the auditory channel to prevent the consciousness from becoming withdrawn, which would result in mere sleep.
In such a way, during yoga Nidra the senses disconnect, and we can experience the fifth stage of Patanjali yoga, known as pratyahara.

The mind needs the training to enter the state of yoga Nidra; otherwise, there is practically no difference between yoga Nidra and sleep.
This practice generally lasts for twenty to forty minutes. The practitioner lies down in shavasana and concentrates only on the instructions given by the facilitator.

The next step is the choice of a sankalpa or resolve. Each practitioner can choose their sankalpa according to their needs and inclination. It is crucial that the wording are precise and clear; otherwise, the resolve won’t penetrate the subconscious mind.
After the sankalpa, begins the rotation of consciousness through the different body parts. There are only three requirements to be fulfilled during this stage: remain aware, listen to the voice, and move the mind very rapidly according to the instructions.
The rotation of consciousness in yoga Nidra proceeds in a definite sequence, and it has to be automatic, spontaneous, and thorough.
After the rotation of consciousness has been completed, physical relaxation is continued and achieved by drawing attention to the breath. In this practice, one maintains awareness of the breath; there should be no attempt to force or change it.

Next comes relaxation on the plane of feelings and emotions.
Feelings that are intensely physical or emotional are recalled or awakened, experienced fully, then removed.
The instructor uses pairs of opposite sensations to achieve this stage: heat and cold, heaviness and lightness, pain and pleasure, joy and sorrow, love and hate.

The last stage of yoga Nidra induces mental relaxation. In this part of the practice, the student visualizes the images named or described by the instructor.
The visualization practice usually ends with an image that evokes profound feelings of peace and calmness. This image makes the unconscious mind very receptive to positive thoughts and suggestions.
Therefore, the practice of yoga Nidra ends with the repetition of the resolve. Then the facilitator gradually brings the mind from psychic sleep to the waking state.