According to one Norse myth, the gods needed a wall. Asgard, their kingdom, had once been surrounded by barricades, but a war had destroyed them. When the gods decided to erect a new wall, a builder appeared out of nowhere and offered his services. Loki, the trickster, suggested that the gods accept his proposal but set an impossible deadline. When time ran out, they could send him on his way, thereby getting the lion’s share of the wall for free.

The builder accepted the terms and set to work. Accompanied by his trusty horse, he made quick work of…