The Prose Edda on Hymer
The Younger Edda: > Chapter Xiv. > Thor'S Adventures.
attestation: Hymer said Thor was too small and young to be useful on the fishing trip
"Hymer answered that he would get but little help from Thor, as he was so small and young"
attestation: Hymer warned that they had gone so far out it was dangerous because of the Midgard-serpent
"Then said Hymer that they had come so far out that it was dangerous to stay there, for the Midgard-serpent"
attestation: Hymer changed color and grew pale from fear, then cut Thor's line at the gunwale, letting the serpent escape
"the giant Hymer changed hue and grew pale from fear when he saw the serpent and beheld the water flowing into the boat; but just at the moment when Thor grasped the hammer and lifted it in the air, the giant fumbled for his fishing-knife and cut off Thor's line at the gunwale, whereby the serpent sank back into the sea"