Have you ever woken up but been unable to move; felt a powerful pressure holding you down, gripping you tight? Haruki Murakami has, and he describes it like this: "I was having a repulsive dream — a dark, slimy dream. ... After I awoke, my breath came in painful gasps for a time. My arms and legs felt paralyzed. I lay there immobilized, listening to my own labored breathing, as if I were stretched out full-length on the floor of a huge cavern."
In this excerpt from the short story "Sleep" from his "The Elephant Vanishes" collection, Murakami is describing an episode of sleep paralysis, which is better known in Japan as kanashibari (literally, "bound in metal").
In other cultures, the experience has been attributed to a ghost (China and Korea), a demon feeding on the living (Fiji) and, in the southern United States, to a witch.