Amazon Rainforest
Most of the letters date back to 1953 and chronicle Burroughs' visit to the Amazon rainforest in search of yagé (ayahuasca), a plant with near-mythical hallucinogenic and some say telepathic qualities. Along the way, Burroughs and Ginsberg share other stories and anecdotes, including some concepts Burroughs would later use in novels such as Naked Lunch. The book ends with further correspondence written in 1960 detailing Ginsberg's experiments with yagé.
Read more about this topic: The Yage Letters