Tuva or Bust! (1991) is a book by Ralph Leighton about the author and his friend Richard Feynman's attempt to travel to Tuva. The introduction explains how Feynman challenged Leighton, at the time a high school math teacher, "Whatever happened to Tannu Tuva?" Since Feynman had a reputation as a prankster, Leighton assumed it was made up. But the country existed, and the pair became fascinated with this hard-to-reach destination in the middle of Asia, which had become a republic in the Soviet Union. They made it a goal to travel there, which, for Americans in the late 1970s and early 1980s, was extremely difficult.