The Prose Edda

"King Gylfe was a wise man and skilled in the black art. He wondered much that the asa-folk was so mighty in knowledge, that all things went after their will. He thought to himself whether this could come from their own nature, or whether the cause must be sought for among the gods whom they worshiped. He therefore undertook a journey to Asgard. He went secretly, having assumed the likeness of an old man, and striving thus to disguise himself. But the asas were wiser, for they see into the future, and, foreseeing his journey before he came, they received him with an eye-deceit. So when he came into the burg he saw there a hall so high that he could hardly look over it. Its roof was thatched with golden shields as with shingles..."