Yage is the Banisteriopsis caapi vine. Back in 1953, William Burroughs experimented with yage and wrote a series of letters to Allen Ginsburg describing his experiences with the hallucinogen (and with Peruvian boys, who rolled the old poof for his money, eyeglasses, &c.). I never had a chance to try this one myself, but the jaguar definitely looks happy.

Via IFL Science.