Banisteripsis capi (ayahuasca)
Yage is made from a South American vine and used by natives of Brazil in male rites of passage and by shamans in religious ceremonies to enhance their perceptions. Predictably, it's hallucinogenic: The stuff contains two of the most powerful natural MAO inhibitors, harmine and harmoline. Small doses produce euphoria and empathy and enhance sex remarkably (for the user). In larger amounts it is quite dangerous and is not recommended without doctor's supervision in any dosage.