This is the authoritative text book of Yoga, one of the six systems of Indian philosophy. Sanskrit Text and translation with commentary which provides a full picture of what Yoga is, what its aims are, how it can be practised, and what liberation of the soul means.
Strength is life, weakness is death. Strength is felicity, life eternal, immortal. Weakness is constant strain and misery; weakness is death.
-Swami Vivekananda