Fanny Paul’s “device for inducing sleep,” patented in 1885, works on a simple principle: It restricts blood flow to the brain. Worry “quickens the action of the heart,” which excites the nervous system; by putting a collar around the neck and tightening it with a screw, the insomniac “slightly modifies” the circulation “and thereby reduce[s] the activity of the brain in order that sleep may ensue.”

“I have experimented with different degrees of pressure upon the arteries and veins of the neck,” Paul wrote, “and find that … very soon after this takes place the nervous system becomes soothed and quieted, and sleep follows almost immediately.”