In the Amazon rainforest there grow two plants: the mariri (Banisteriopsi caapi) and the chacrona (Psychotria viridis), which have been used by native Indians for hundreds of years to make an infusion. The infusion, known as ‘hoasca tea’, is no ordinary herbal brew but one with psychoactive properties. The leaves of these plants contain dimethyltryptamine (DMT), which has hallucinogenic...