When Thor came to Geirrod, he and his companion were shown to the guest-room, where lodgings were given them, but there was but one seat, and on that Thor sat down. Then he became aware that the seat was raised under him toward the roof. He put the Gridarvol against the rafters, and pressed himself down against the seat. Then was heard a great crash, which was followed by a loud screaming. Under the seat were Geirrod’s daughters, Gjalp and Greip, and he had broken the backs of both of them.

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