Knock-out powder is a chemical substance which causes those who inhale it to enter a deep sleep.
History and specifics[]
The Tol people of Neesan used a knock-out powder which they called the Sleep of Eternity. (TOS comic: "The Cosmic Cavemen")
Robot drones appeared to shoot knock-out powder at Spock and James T. Kirk from a cave on Raylo in the 2260s. Spock revived within a few minutes. Kirk awoke only after receiving a hypospray shot from Doctor Leonard McCoy, but had become hypnotized. Later, Doctor Rycho threw knock-out powder at Spock and McCoy, incapacitating both officers immediately. (TOS comic: "Rescue at Raylo")