("yoga slumber") The Goddess's epithet appears in
the first episode of the Devi Mahatmya, the oldest and most authoritative
document on the Goddess's mythology.
In this episode, the Goddess uses her power of illusion to
lull Vishnu into a coma, rendering him unconscious to Brahma's screams for aid
when he is threatened by the demons Madhu and Kaitabha.
When Brahma praises the Goddess, she withdraws her yogic
slumber from Vishnu, allowing him to restore consciousness and save Brahma by
destroying the demons.
You may also want to read more about Hinduism here.
Be sure to check out my writings on religion here.