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:
The early practice of Jain yoga seems to have been divided into several types, including meditation (dhyāna), abandonment of the body (kāyotsarga), contemplation (anuprekṣā), and reflection (bhāvanā). Some of the earliest sources for Jain yoga are the Uttarādhyayana-sūtra, the Āvaśyaka-sūtra, the Sthananga Sutra (c. 2nd century BCE). Later works include Kundakunda's Vārassa-aṇuvekkhā (“Twelve Contemplations”, c. 1st century BCE to 1st century CE), Haribhadra's Yogadṛṣṭisamuccya (8th century) and the Yogaśāstra of Hemachandra (12th century). Later forms of Jain yoga adopted Hindu influences, such as ideas from Patanjali's yoga and later Tantric yoga (in the works of Haribhadra and Hemachandra respectively). The Jains also developed a progressive path to liberation through yogic praxis, outlining several levels of virtue called gunasthanas.
According to Crangle, some researchers have favoured a linear theory, which attempts "to interpret the origin and early development of Indian contemplative practices as a sequential growth from an Aryan genesis",[note 4] just like traditional Hinduism regards the Vedas to be the ultimate source of all spiritual knowledge.[note 5] Thomas McEvilley favors a composite model where pre-Aryan yoga prototype existed in the pre-Vedic period and its refinement began in the Vedic period.
Equipment required? No. You don't need any equipment because you'll rely on your own body weight for resistance. But you'll probably want to use a yoga mat to keep you from sliding around in standing poses, and to cushion you while in seated and lying positions. Other, optional equipment includes a yoga ball for balance, a yoga block or two, and straps to help you reach for your feet or link your hands behind your back.