The credit of collating, systemising, and codifying the entire philosophy of yoga goes to Sage Patanjali, regarded as the codifier of the subject of yoga. Historically, Patanjali may have lived between 500 and 200 B.C. He chose to write on three subjects: grammar, medicine and yoga. The Yoga Sūtra, his culminating work, is his distillation of human knowledge. His 196 aphorisms or sutra’s cover all aspects of life, beginning with a prescribed code of conduct, and ending with man’s vision of his true Self.

The eight limbs/ aspects of Yoga as enumerated by Patanjali are:

• Yama – Ethical disciplines that transcend caste, creed, country, age and time. The five yama are ahimsā, (non-violence), satya(truth), asteya (non-stealing), brahmacharya(continence), and aparigraha (non-coveting)
• Niyama – Rules of conduct for self-purification through individual discipline. The 5 niyama are śaucha (purity), santosa (contentment), tapas (ardour or austerity), svādhyāya (study of Self), Iśvara pranidhāna (dedications to the Lord).
• Āsana – āsana are not merely gymnastic excercises; they are postures that have been evolved over the centuries so as to exercise every muscle, nerve and gland in the body. They secure a fine physique, which is strong and elastic, without being muscle-bound, and they keep the body free from disease. They reduce fatigue and soothe the nerves. But their real importance lie in the way they train and discipline the mind. The yogi conquers the body by the practice of āsana, and makes it a fit vehicle for the spirit. Where doe the body end and the mind begin? Where does the mind end and the spirit begin? They cannot be divided as they are inter-related but different aspects of the same all-pervading consciousness.
• Prānayāma – Prāna means breath, respiration, life, vitality, wind, energy or strength. Āyāma means length, expansion, stretching or restraint. Prānayāma thus connotes extension of breath and its control. This control is over all the functions of breathing, namely: inhalation (pūraka), exhalation (rechaka), and retention (kumbhaka). Prānayāma is the hub around which the hub of life revolves.

“As lions, elephants and tigers are tamed very slowly and cautiously, so should prāna be brought under control very slowly in gradation measured according to one’s capacity and physical limitations. Otherwise it will kill the practitioner.” warns the Hatha Yoga Pradīpika.

• Pratyāhāra – withdrawal and emancipation of the mind from the domination of the senses and exterior objects.
• Dhāranā – When the body has been tempered by āsana, when the mind has been refined by the fire of Prānayāma, and when the senses have been brought under control by Pratyāhāra, the sādhaka reaches this sixth stage. Here he is concentrated wholly on a single point or on a task in which he is completely engrossed.
• Dhyāna – When oil is pored from one vessel to another, one can observe the steady, constant flow. When the flow of concentration is uninterrupted, the state that arises is dhyāna.
• Samādhi – Samādhi is the end of the sādhaka’s quest. At the peak of his meditation, he passes into the state of Samādhi where his body and senses are at rest as if asleep, his faculties of mind and reason are alert as if he is awake, yet he has gone beyond consciousness.