The Sturlunga, Landnama, and Holmveria Sagas.
Two priests determined to solve the mystery of this unapproachable valley, the Aradal, or Thoris-thal, with its rich meadows and gigantic inhabitants, and made an expedition for this purpose in 1664. They reached a point where the glaciers fell off into a valley so deep that they could not see whether there were meadows at the bottom or not, and the slope was so rapid that it was impossible to descend.
Voyage en Islande; Atlas Historique; t. ii., pl. 130-133.
Iceland: its Scenes and Sagas: pp. 97, 98.
Page 113.