In 1971, five hippies made a trek through the Amazon looking for rare psychedelic drugs. One of them was Terence McKenna, who, along with his brother Dennis, would go on to change the way Americans thought about “magic mushrooms” forever. We talk to John O’Connor, author of “A Short, Strange Trip: An Untold Story of Magic Mushrooms, Madness, and a Search for the Meaning of Life in the Amazon.”