Then went Thor to the river which is called Vimer, and which is the largest of all rivers. He buckled on the belt of strength and stemmed the wild torrent with Gridarvol, but Loke held himself fast in Megingjard. When Thor had come into the middle of the stream, the river waxed so greatly that the waves dashed over his shoulders. Then quoth Thor:

Wax not Vimer,
Since I intend to wade
To the gards of giants.
Know, if you wax,
Then waxes my asa-might
As high, as the heavens.

Then Thor looked up and saw in a cleft Gjalp, the daughter of Geirrod, standing on both sides of the stream, and causing its growth. Then took he up out of the river a huge stone and threw at her, saying: At its source the stream must be stemmed. He was not wont to miss his mark. At the same time he reached the river bank and got hold of a shrub, and so he got out of the river. Hence comes the adage that a shrub saved Thor.

- Prose Edda (Thor's Journey to Geirrod's)