This should really be titled "sex magic" but the person who wrote it down lived in a more prudish age than we do ;-)
Around 1820 there were two young men who lived on a farm in the Eyjafjörður area. They were studying sorcery in secret but were found out when one evening after dark one of them came into the common room and walked up to a young woman who was sitting there and kissed her passionately. She was surprised by this, especially as she thought she heard something rattling in the man’s mouth as he kissed her, and because all of a sudden she began to feel aroused. In the room were also two motherless lambs that were being fostered inside the warmth of the house, an ewe and a ram.
She thought quickly and said: “If you are playing a trick on me, it shall affect the ewe-lamb instead.” Immediately the ewe came into heat and kept offering herself to the ram all night long.
When the girl noticed this and felt the passion she had almost succumbed to subside, she questioned the man and wouldn’t let him go until he admitted that he had put piece of lead with some magic runes on it in his mouth and then kissed her in order to get her into bed with him.