yatrasrama-padany ubhayato nabhibhir drsac-cakrais cakra-nadi nama sarit-pravara sarvatah pavitri-karoti.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In Pulaha-asrama is the Gandaki River, which is the best of all rivers. The salagrama-sila, the marble pebbles, purify all those places. On each and every marble pebble, up and down, circles like navels are visible.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Salagrama-sila refers to pebbles that appear like stones with circles marked up and down. These are available in the river known as Gandaki-nadi. Wherever the waters of this river flow, the place becomes immediately sanctified.