Until the time of Bhagavad Gita, the knowledge of yoga was confined to literature in the sacred texts. In the later times a more practical approach towards its practice started emerging. Many teachers and gurus started practicing yoga and shared their practical experiences by the word of mouth.
Since the knowledge of yoga was propagated by the word of mouth, its development wasn’t structured. Before its systematization, yoga was a collection of unrelated and varied techniques composed of personal beliefs and superstitions.
Maharshi Patanjali was the first one to compile and systematize yoga. He wrote Yoga Sutras, which was believed to be written before the birth of Christ. Even today, the text Yoga Sutras of Patanjali is considered authoritative and the greatest contribution to the world of Raja yoga.
The yoga sutras of patanjali have 196 verses. Within these verses, the whole concept of Raja Yoga (Yoga of the mind) has been explained in a scientific method. The description of mind, its modifications, techniques to tame it are very well explained in these sutras. After Patanjali, many more texts and commentaries were written on yoga. Though the intention was good, due to lack of clarity, they caused more confusion, controversy and speculation.
After Patanjali, contribution of Shankaracharya to yoga is widely recognized and lauded. He personally interpreted twelve different Upanishads, Bhagavad Gita. His original works on Yoga include Viveka Chudamani (Crest Jewel of Wisdom), Aparokshanubhuti (Direct Experience of Reality) and the Atma- bodha (Knowledge of the Self). These texts are absolute masterpieces and a treasure of knowledge. These texts have much authority in them since Shankaracharya wrote them out of his personal experience rather than relying on intellectual analysis of ancient texts.
After Shankaracharya, there were many great yogis and scholars who contributed their share of invaluable experience throughout the middle age. Bhakti yogis such as Kabir, Tulsidas, Chaitanya Mahaprabhu, Nam Dev and many more wrote wonderful poetry which strike the chords of devotion even today. These yogis interspersed their devotion with clear practical advice on the path of bhakti yoga and other paths.
Throughout the ages Hatha Yoga texts were written in plenty by great yogis. Amongst them Hatha Yoga Pradipika, Shiva Samhita and Gherand Samhita are well known. In these texts, asana, pranayama, mudras, bandhas and other yoga practices were clearly explained. Though these practices were all with regards to the practices done by the physical body, they were a means to achieve higher ideals, which first need a healthy body.
Prominent names of sages of ancient times who contributed to yoga were Gorakhnath, Matsyendranath, Janaka, Yajnavalkya, Ashtavakra and Vyasa. Ramakrishna Paramahamsa, Swami Vivekananda, Ramana Maharshi, Swami Sivananda, Swami Satyananda are popular names of the recent times. The list of yogis who have contributed to yoga is endless and the number of books and commentaries written by them are also in thousands.
Other noted works on yoga include Ashtavakra Gita (for advanced states of meditation), Anu Gita (further explanation of the Bhagavad Gita), Brahma Sutras (essence of the Upanishads), Vyasabhasya (commentary on Patanjali’s Yoga Sutras), Narada’s Bhakti Sutras (rules for bhakti yoga).
The practice of yoga has nothing to do with its history, neither does reading a traditional text induce any yogic qualities within us. Referring to the history of yoga and reading the traditional texts help us to only understand its essence, but not to live it by experience. It is a fact that You will learn more from a yoga class of a novice yoga teacher than from reading the entire vedas. Yoga is 100% practice. Regular practice, guidance of a competent guru are far better resources of indulging in yoga than the scriptures.