Shandilya Upanishad has given more observance than many other yogic texts. Shandilya Upanishad gives broader experience and opportunities to the practitioner to perfect niyama, comfortably.
One day, while he was performing his daily ablutions, Maharshi Valmiki saw a pair of krauncha birds (cranes) on the branch of a tree and having their good lines, singing sweetly.