India's spiritual masters, and the teachings we study at the ashram

Indian tradition honours Veda Vyasa as the sage who arranged the Vedas and composed the Mahabharata, the great epic that contains the Bhagavad Gita. Guru Purnima, the full-moon day on which India honours its teachers, is also kept as Vyasa Purnima in his name.

Tradition also gives his name to the Yoga Bhashya, the oldest surviving commentary on Patanjali's Yoga Sutras. Scholars still debate who wrote it, but students of the Sutras have read them through it for well over a thousand years.

Almost nothing is known for certain about Patanjali's life. Tradition holds him to be an incarnation of Adishesha, the serpent on which Vishnu rests, which is why statues show him with a serpent's hood above his head.

What has come down to us is his text: the earliest surviving systematic account of yoga as a discipline of the mind, so concise that it has drawn commentaries for more than fifteen centuries, from Vyasa to Vivekananda and Iyengar.

Swatmarama was a yogi of the Nath tradition. He opens his book by naming the masters before him, from Adinatha (Shiva) to Matsyendranath and Gorakhnath, and presents Hatha Yoga as a stairway to Raja Yoga, the yoga of the mind described by Patanjali.

The Hatha Yoga Pradipika gathered older teachings into one practical manual, and it remains the best-known classical text on Hatha Yoga, the tradition Rishikesh Yogpeeth teaches.

Born Narendranath Datta in Calcutta on 12 January 1863, he became the foremost disciple of the mystic Sri Ramakrishna. His address to the World's Parliament of Religions in Chicago in September 1893 made him one of the first teachers of Vedanta and yoga to reach a wide Western audience.

He founded the Ramakrishna Mission in 1897 and died at Belur Math in 1902, aged 39. India marks his birthday every year as National Youth Day.

Born Kuppuswami in Pattamadai, Tamil Nadu, on 8 September 1887, he practised as a doctor in Malaya before leaving medicine for the spiritual life. He came to Rishikesh, took sannyasa here in 1924, and in 1936 founded the Divine Life Society on the banks of the Ganga, where he taught until 1963.

His disciples carried yoga around the world. Among them were Swami Vishnudevananda, Swami Satyananda Saraswati, founder of the Bihar School of Yoga, and Swami Satchidananda.

Bellur Krishnamachar Sundararaja Iyengar was a sickly child when he began learning yoga in 1934 from his brother-in-law, T. Krishnamacharya, in Mysore. He settled in Pune, where he taught for more than seven decades and opened the Ramamani Iyengar Memorial Yoga Institute in 1975.

TIME named him one of the 100 most influential people in the world in 2004, and India awarded him the Padma Shri, Padma Bhushan and Padma Vibhushan. He died in Pune on 20 August 2014, aged 95.