<P> The hymns in Book 2 of the Shvetashvatara Upanishad, another late first millennium BCE text, states a procedure in which the body is held in upright posture, the breath is restrained and mind is meditatively focussed, preferably inside a cave or a place that is simple, plain, of silence or gently flowing water, with no noises nor harsh winds . </P> <P> The Maitrayaniya Upanishad, likely composed in a later century than Katha and Shvetashvatara Upanishads but before Patanjali's Yoga Sutra, mentions sixfold yoga method--breath control (pranayama), introspective withdrawal of senses (pratyahara), meditation (dhyana), mind concentration (dharana), philosophical inquiry / creative reasoning (tarka), and absorption / intense spiritual union (samadhi). </P> <P> In addition to the Yoga discussion in above Principal Upanishads, twenty Yoga Upanishads as well as related texts such as Yoga Vasistha, composed in 1st and 2nd millennium CE, discuss Yoga methods . </P> <P> Yoga is discussed in the ancient foundational Sutras of Hindu philosophy . The Vaiśeṣika Sūtra of the Vaisheshika school of Hinduism, dated to have been composed sometime between 6th and 2nd century BCE discusses Yoga . According to Johannes Bronkhorst, an Indologist known for his studies on early Buddhism and Hinduism and a professor at the University of Lausanne, Vaiśeṣika Sūtra describes Yoga as "a state where the mind resides only in the soul and therefore not in the senses". This is equivalent to pratyahara or withdrawal of the senses, and the ancient Sutra asserts that this leads to an absence of sukha (happiness) and dukkha (suffering), then describes additional yogic meditation steps in the journey towards the state of spiritual liberation . </P>

Where did yoga originated and how long ago