The serpent is a yogic metaphor for death and eternal life. Before 500 BCE, the Brihadaranyaka Upanishad (4.4.7) said that the immortal soul sheds its mortal body “like a snake sloughs off its skin”. The serpent’s skins or sheaths, says David Gordon White in The Alchemical Body, are the layers between humanity and divinity, embodiment and essence1.
The sleeping “serpentine” power (kundalini) must arise out of the sheaths (kancukas) that bind and cover the soul (atman). The yogi practices techniques of pranayama (breath control) to awaken the sleeping serpent (kundalini) at the base of the spine in the subtle yogic body. As the kundalini serpent awakens, a series of subtler yogic bodies arise out of the ashes of death. Like peeling back the layers of an onion to get to the central essence, the advanced yogin achieves ecstasy (samadhi); the Siddha (liberated soul) is preserved in endless bliss and immortality.
What dies? The gross body is a husk that is shed like the skin of a snake. Human creatures are endowed with kancukas (sheaths) while in the bosom of Maya (illusion), the material and impure world. The Hindus and Buddhists devised the concept and practice of pranayama for the yogi to raise the serpent from the sheaths of the subtle yogic body. As White explains the purpose of the serpent metaphor in his book The Alchemical Body: The Siddha Traditions of Medieval India: “Here, [the supreme soul’s] yogic sleep is the divine model for samadhi of the human yogin who has withdrawn all breath, seed, and consciousness to concentrate these into a single point of pure being-consciousness-bliss”.
In Hindu and Buddhist yoga, the serpent metaphor represents death and eternal life. The snake sheds dead skin and reveals an innermost self. Likewise, the yogi sheds layers of his subtle body to reveal soul essence. The layers of the subtle body are removed, through pranayama, and die off until only an eternal essence remains, the atman (soul). Then the Siddha (liberated, perfected one) dwells in the abode of the gods in endless bliss of samadhi and immortality.
1 White, David Gordon. The Alchemical Body: Siddha Traditions in Medieval India. University of Chicago Press. 1996. Print. p214