The Nath Sampradaya and the hatha yoga literature that grew up closely associated with it teach that the physical body itself can be refined and perfected into a deathless, transformed condition, a siddha deha, rather than treated as a temporary vessel to be transcended or left behind at liberation. The Alchemical Body, a study of this tradition, describes hatha yoga on this model as the actual mechanism of transformation rather than a preparatory discipline undertaken to steady the mind before a separate practice of meditation begins, so that postures, breath control and specific internal techniques are understood to work directly on the body's substance rather than merely on the practitioner's mental state. Roots of Yoga, a study and translation of early hatha yoga texts, traces how this literature's vocabulary of refining, fixing and perfecting bodily substance runs directly parallel to the vocabulary of rasayana, the Indian alchemical tradition concerned with transmuting base metals into gold, a parallel treated as more than coincidental, since both traditions describe their respective transformations using shared technical terms for purification and fixation. On this account the goal is not departure from embodiment at death but a body made deathless in itself, a claim that marks a clear departure from Vedantic traditions that treat liberation as release from the body altogether.