The term yoga nidra is derived from two Sanskrit words,yoga meaning union or one-pointed awareness, and nidra meaning sleep. During the practice of yoga nidra, one appears to be asleep, but the consciousness is functioning at a deeper level of awareness. This means that even when you sleep, your self is awake and aware. For this reason, yoga nidra is often referred to as deep relaxation/sleepless sleep/yogic sleep/psychic sleep/transcendental sleep/dynamic sleep/conscious sleep or scientific sleep with inner awareness. Yoga nidra is a process by which one can travel from the conscious to the unconscious through the subconscious. Yoga nidra is one of the pratyahara practices, where one withdraws the awareness from external sources and gradually enters into chitta, which ultimately leads to dhyana and samadhi too.
Yoga nidra is a practice derived by Swami Satyananda Saraswati from ancient sources. It has been discussed in the Vedas and Puranas, such as Devi Mahatmya and the Bhagavata Purana. Vishnu, the sleeping Lord, reclines on Sheshanaga, the multi-hooded serpent, in yoga nidra. Of the four states of consciousness, waking, dreaming, deep sleep and super consciousness, as expounded in the Upanishads, yoga nidra refers specifically to the conscious awareness of the deep sleep state, referred to as prajna in the Mandukya Upanishad. Maharshi Patanjali and the authors of the hatha yoga texts and other literatures might have been influenced by the Vedas, Upanishads and Puranas. It has been found that in some texts there are indications and discussions of the yoga nidra practice, such as Patanjali's Yoga Sutras (PYS) and Hatha Yoga Pradipika. Let us discuss how Maharshi Patanjali has indicated the practice of yoga nidra in his Yoga Sutras.
Patanjali's Yoga Sutras is said to be one of the authentic yogic texts accepted world-wide. It was composed by Maharshi Patanjali between the 2nd and 4th century BC, and there are some direct and indirect indications of yoga nidra in different chapters.
In Samadhi Pada, Patanjali mentions one technique by which the sadhaka can make his mind steady and prevent it from chitta vikshepa, distraction. In the chitta, the individual consciousness, there are nine types of hindrances: (i) vyadhi, disease, (ii) styana, dullness, (iii) samashaya, doubt, (iv) pramada, carelessness, procrastination, (v) alasya, laziness, (vi) avirati, strong attachment, (vii) bhrantidarshana, delusion, erroneous perception, (viii) alabdhabhoomikatva, inability to achieve a finer state, (ix) anavasthitatva, instability. To remedy chitta vikshepa one must choose and practice a technique suitable for oneself.
For this reason, Patanjali mentions many techniques. Amongst these, there is one technique which is related to yoga nidra: Svapnanidraajnaanaalambanam vaa (PYS, 1:38)*, which means that "The mind can be made steady by giving it the knowledge of dream and sleep for support." In order to gain knowledge of sleep and especially dream, one must have the ability to analyse the dream. For this reason, one must be aware of the dream during sleep, and this is the indication of the practice of yoga nidra in Patanjali's Yoga Sutras.
We need to understand the nature of the dreaming state in order to fully comprehend the use of visualization in yoga nidra. In the usual state of dreaming, the content and expression of dreams are related to the spontaneous build-up and release of psychic tension from the subconscious, as well as the awakening and expression of deeper unconscious instincts and drives. However, in the visualization practices of yoga nidra, recognition and release are voluntarily induced as we create the dreams consciously. In dreaming, we obtain knowledge about our subconscious and unconscious. The unconscious is the guiding force behind our every action, i.e. samskara. Bringing the awareness into it, we understand the nature and root cause of hindrances or chitta vikshepa, mental fickleness.
In Vibhuti Pada also there are a few sutras which refer to yoga nidra. Let us analyse them as follows. Parinaama trayasamyamaadateetaanaagatajnaanam (PYS, 3:16), which means "By performing samyama on the three transformations, knowledge of past and future (arises)." By practicing samyama on the three transformations of one's own consciousness in samadhi, awareness becomes subtle. By the practice of yoga nidra one can enter into the unconscious state and awaken a tiny point of awareness in that total unconsciousness.
As we know, everything is already stored in the unconscious in the form of samskaras. Therefore, by developing awareness of the unconscious, it is possible to know not only the past and future but also one's past lives. Samskaarasaakshaatkaranaat poorvajaatijnaanam (PYS, 3:18).
Sopakramam nirupakramam cha karma tatsamyamaad aparaanta-jnaanamarishtebhyo vaa (PYS, 3:23), that means by performing samyama on the early maturation and late maturation of karmaphala, the fruits of karma, one can gain knowledge of death, as well as by studying omens. Here, the reference to omens may have relevance to yoga nidra. Only the conscious dreamer can understand the omens presented to the conscious mind.
Raja yoga or ashtanga yoga has been composed by Maharshi Patanjali in a very systematic way. It gives a new vision or guideline to sadhakas and others. The eight-fold path of raja yoga is as follows: (i) yama, social code and conduct, self-restraint, (ii) niyama, personal code and conduct, self-observance, (iii) asana, physical posture, (iv) pranayama, breath control, (v) pratyahara, withdrawing the mind from the senses, (vi) dharana, concentration, (vii) dhyana, meditation or oneness with the object, (viii) samadhi, self-realization or super consciousness.
By following these systematic steps of raja yoga the sadhaka can easily attain success in yoga. Yoga nidra is one form of raja yoga. By the practice of yoga nidra, a sadhaka can reach his final destination of samadhi. Let us briefly discuss how yoga nidra is simplified raja yoga.
When dharana deepens, the object becomes constant and the next step is dhyana, Tatra pratyayaikataanataa dhyaanam (PYS, 3:2). Yoga nidra is a technique which can be used to awaken divine faculties and is a way to enter samadhi. By the practice of the raja yoga techniques, particularly yoga nidra, we try to become aware of the subconscious and unconscious state and ultimately enter into the state of super-consciousness. That is why yoga nidra is the doorway to samadhi.
Tadevaarthamaatranirbhaasam svaroopashoonyamiva samaadhih (PYS, 3:3), means "That state becomes samadhi when there is only the object appearing without the consciousness of one's own self." When the subject is clearly perceived in its mere essence, that is called samadhi.
By the practice of yoga nidra, we enter from the conscious through the subconscious into the unconscious. By the gradual practice of yoga nidra, when one awakens a tiny point of awareness in that total unconscious state, it is called super-consciousness, and this is the state of samadhi in raja yoga too.
Patanjali's yoga is a systematic discipline which can lead a sadhaka from the simple to the complex. We start from yama, niyama, asana, pranayama, pratyahara, dharana, dhyana and reach samadhi, which is the culmination of yoga. Yoga nidra can also lead to dharana and dhyana and ultimately to samadhi, although it is basically one of the pratyahara practices. If we really practice, we can experience all the steps of Patanjali's yoga. In the form of Swami Satyananda's yoga nidra practice we precede from the preparation or internalisation to the sankalpa/resolve, rotation of consciousness, breath awareness, awareness of opposite feelings and sensations, visualization, resolve, to the end of the practice or externalisation.
In raja yoga, an aspirant follows its systematic steps. First, he practices yama and niyama, and only when he is established in asana can he practice pranayama, so on and so forth. In the form of yoga nidra which is taught by Swami Satyananda, we also find different levels of practice, for beginners, intermediate and advanced practitioners or groups. In yoga nidra we can visualize mantras, yantras, prana, chakras, their letters, deities, the ishta devata or guru, and the deep-rooted samskaras can also be brought out to the conscious state. Psychosomatic problems can be managed by bringing their root cause to the conscious mind from the unconscious. Lastly, the practitioner can awaken a tiny point of awareness in that total unconsciousness and that is super consciousness or the state of samadhi. This happens in raja yoga too. Therefore, we can say that yoga nidra is nothing but simplified raja yoga.
* Quotations from Four Chapters on Freedom by Swami Satyananda Saraswati, published by Yoga Publications Trust.