King Puruva once asked a saint, "How can a person be
cleansed of his sins and go to heaven without performing yajnas?"
The sage said, "Only the river Narmada can do this, but she is in
heaven and will have to be brought to earth." Puruva performed a long
penance to please Shiva. When Shiva appeared he requested him to bring
Narmada to earth. Shiva asked Narmada to descend on earth. But Narmada
needed a base from which she could emerge on earth.
Shiva asked the mountains as to who was capable of providing Narmada
with a base. The Maikal range of mountains agreed to it. When Narmada
came on earth, she flooded all the mountains and forests. She was asked to
control her force. Then Puruva purified his ancestors' souls by cleansing
himself in the waters of the Narmada.