Ascetic practices, concentration and bodily postures described in the Vedas may have been precursors to yoga. According to Geoffrey Samuel, "Our best evidence to date suggests that [yogic] practices developed in the same ascetic circles as the early sramana movements (Buddhists, Jainas and Ajivikas), probably in around the sixth and fifth centuries BCE."
Yogaśataka a Jain work by Haribhadra Suri 6th century CE "With conviction, the lords of Yogins have in our doctrine defined yoga as the concurrence (sambandhah) of the three [correct knowledge (sajjñana), correct doctrine (saddarsana) and correct conduct (saccaritra)] beginning with correct knowledge, since [thereby arises] conjunction with liberation....In common usage this [term] yoga also [denotes the soul’s] contact with the causes of these [three], due to the common usage of the cause for the effect. (2, 4).
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.
One of the best known early expressions of Brahmanical Yoga thought is the Yoga Sutras of Patanjali , the original name of which may have been the Pātañjalayogaśāstra-sāṃkhya-pravacana (c. sometime between 325 - 425) which some scholars now believe included both the sutras and a commentary. As the name suggests, the metaphysical basis for this text is the Indian philosophy termed Sāṃkhya. This atheistic school is mentioned in Kauṭilya's Arthashastra as one of the three categories of anviksikis (philosophies) along with Yoga and Cārvāka. The two schools have some differences as well. Yoga accepted the conception of "personal god", while Samkhya developed as a rationalist, non-theistic/atheistic system of Hindu philosophy. Sometimes Patanjali's system is referred to as Seshvara Samkhya in contradistinction to Kapila's Nirivara Samkhya. The parallels between Yoga and Samkhya were so close that Max Müller says that "the two philosophies were in popular parlance distinguished from each other as Samkhya with and Samkhya without a Lord." https://buzzingoffer.tumblr.com/