Haṭha Yoga
हठयोग
RESOURCE ONE
Haṭha Yoga
Iḍā is the Gaṅga of the lower world, piṅgalā the river Yamunā, and between iḍā and piṅgalā is sushumṇā, the subtle river Sarasvatī. It is said that to bathe in the confluence of the three rivers leads to the Great Result.§
Śukla Yajur Veda, Trishikhi Brāhmaṇa Upanishad, 316-317§