What is often referred to as Classical Yoga or Astanga Yoga (Yoga of eight limbs) is mainly the type of Yoga outlined in the highly influential Yoga Sutras of Patanjali. The origins of the Classical Yoga tradition are unclear, though early discussions of the term appear in the Upanishads. The name "Rāja yoga" (yoga of kings) originally denoted the ultimate goal of yoga, samadhi, but was popularised by Vivekananda as a common name for Ashtanga Yoga,[note 19] the eight limbs to be practised to attain samadhi, as described in the Yoga Sutras. Yoga is also considered as one of the orthodox philosophical schools (darsanas) of Hinduism (those which accept the Vedas as source of knowledge).
^ On the dates of the Pali canon, Gregory Schopen writes, "We know, and have known for some time, that the Pali canon as we have it — and it is generally conceded to be our oldest source — cannot be taken back further than the last quarter of the first century BCE, the date of the Alu-vihara redaction, the earliest redaction we can have some knowledge of, and that — for a critical history — it can serve, at the very most, only as a source for the Buddhism of this period. But we also know that even this is problematic... In fact, it is not until the time of the commentaries of Buddhaghosa, Dhammapala, and others — that is to say, the fifth to sixth centuries CE — that we can know anything definite about the actual contents of [the Pali] canon."
According to Geoffrey Samuel, our "best evidence to date" suggests that yogic practices "developed in the same ascetic circles as the early śramaṇa movements (Buddhists, Jainas and Ajivikas), probably in around the sixth and fifth centuries BCE." This occurred during what is called the ‘Second Urbanisation’ period. According to Mallinson and Singleton, these traditions were the first to use psychophysical techniques, mainly known as dhyana and tapas. but later described as yoga, to strive for the goal of liberation (moksha, nirvana) from samsara (the round of rebirth).
The first known appearance of the word "yoga", with the same meaning as the modern term, is in the Katha Upanishad, probably composed between the fifth and third century BCE, where it is defined as the steady control of the senses, which along with cessation of mental activity, leading to a supreme state.[note 13] Katha Upanishad integrates the monism of early Upanishads with concepts of samkhya and yoga. It defines various levels of existence according to their proximity to the innermost being Ātman. Yoga is therefore seen as a process of interiorization or ascent of consciousness. It is the earliest literary work that highlights the fundamentals of yoga. White states:
^ "application or concentration of the thoughts, abstract contemplation, meditation , (esp.) self-concentration, abstract meditation and mental abstraction practised as a system (as taught by Patañjali and called the yoga philosophy; it is the second of the two sāṃkhya systems, its chief aim being to teach the means by which the human spirit may attain complete union with īśvara or the Supreme Spirit; in the practice of self-concentration it is closely connected with Buddhism". Monier-Williams, A Sanskrit Dictionary (1899)
Śaradatilaka of Lakshmanadesikendra, a Shakta Tantra work 11th century CE "Yogic experts state that yoga is the oneness of the individual soul (jiva) with the atman. Others understand it to be the ascertainment of Siva and the soul as non-different. The scholars of the Agamas say that it is a Knowledge which is of the nature of Siva’s Power. Other scholars say it is the knowledge of the primordial soul." (SaTil 25.1–3b)
Alexander Wynne observes that formless meditation and elemental meditation might have originated in the Upanishadic tradition. The earliest reference to meditation is in the Brihadaranyaka Upanishad, one of the oldest Upanishads. Chandogya Upanishad describes the five kinds of vital energies (prana). Concepts used later in many yoga traditions such as internal sound and veins (nadis) are also described in the Upanishad. Taittiriya Upanishad defines yoga as the mastery of body and senses.
Description of an early form of yoga called nirodhayoga (yoga of cessation) is contained in the Mokshadharma section of the 12th chapter (Shanti Parva) of the Mahabharata (third century BCE). Nirodhayoga emphasizes progressive withdrawal from the contents of empirical consciousness such as thoughts, sensations etc. until purusha (Self) is realized. Terms like vichara (subtle reflection), viveka (discrimination) and others which are similar to Patanjali's terminology are mentioned, but not described. There is no uniform goal of yoga mentioned in the Mahabharata. Separation of self from matter, perceiving Brahman everywhere, entering into Brahman etc. are all described as goals of yoga. Samkhya and yoga are conflated together and some verses describe them as being identical. Mokshadharma also describes an early practice of elemental meditation. Mahabharata defines the purpose of yoga as the experience of uniting the individual ātman with the universal Brahman that pervades all things.
This terse definition hinges on the meaning of three Sanskrit terms. I. K. Taimni translates it as "Yoga is the inhibition (nirodhaḥ) of the modifications (vṛtti) of the mind (citta)".Swami Vivekananda translates the sutra as "Yoga is restraining the mind-stuff (Citta) from taking various forms (Vrittis)." Edwin Bryant explains that, to Patanjali, "Yoga essentially consists of meditative practices culminating in attaining a state of consciousness free from all modes of active or discursive thought, and of eventually attaining a state where consciousness is unaware of any object external to itself, that is, is only aware of its own nature as consciousness unmixed with any other object."
Later developments in the various Buddhist traditions led to new innovations in yogic practices. The Theravada school, while remaining relatively conservative, still developed new ideas on meditation and yogic phenomenology in their later works, the most influential of which is the Visuddhimagga. The Indic meditation teachings of Mahayana Buddhism can be seen in influential texts like the Yogācārabhūmi-Śāstra (compiled c. 4th century). Mahayana meditation practices also developed and adopted new yogic methods, such as the use of mantra and dharani, pure land practices which aimed at rebirth in a pure land or buddhafield, and visualization methods. Chinese Buddhism developed its own methods, such as the Chan practice of Koan introspection and Hua Tou. Likewise, Tantric Buddhism (also Mantrayana, Vajrayana) developed and adopted tantric methods, which remain the basis of the Tibetan Buddhist yogic systems, including the Six yogas of Naropa, Kalacakra, Mahamudra and Dzogchen.
According to Pāṇini, the term yoga can be derived from either of two roots, yujir yoga (to yoke) or yuj samādhau ("to concentrate"). In the context of the Yoga Sutras of Patanjali, the root yuj samādhau (to concentrate) is considered by traditional commentators as the correct etymology. In accordance with Pāṇini, Vyasa who wrote the first commentary on the Yoga Sutras, states that yoga means samādhi (concentration).