In the 1950s, yeti hunting was all the rage among explorers. In 1951, mountaineer Eric Shipton’s expedition to Mt. Everest brought back photos of a mysterious three-toed footprint; in 1954, the Daily Mail sent scientists and mountaineers on a 6-month “Snowman Expedition” to the Himalayas specifically to find the mysterious creature. None of their research was conclusive, but that didn't stop adventure-seekers from trying to find evidence of the yeti's existence.

The U.S. government took the time in 1959 to remind these zealots that if they found a yeti, they couldn't shoot it. Unless it was trying to kill them, of course.

In a state department memo dated December 10, 1959, government officials laid out the regulations that governed yeti hunting in Nepal.

First of all, it was not going to be free. Would-be trackers were ordered to get a permit from the Nepali government, paying 5000 rupees (adjusting for inflation, about $1100 today) for the privilege.

Furthermore, the Nepali government was entitled to any evidence the hunters found. Any photos taken or reports proving the animal’s existence had to be surrendered to the government, and if there was going to be a report “throwing light on the actual existence of the creature,” it couldn’t be given to the press until the government approved it. If the creature was captured, obviously, it would also have to be turned over to the state. Dead or alive.

NARA

And last, and most importantly, that “dead or alive” clause wasn’t permission to go around shooting mythical creatures. Yetis could only be killed or shot in self-defense. Finding the yeti was a scientific pursuit, not a trophy sport.

Why did the U.S. government care? According to the National Archives—which currently has the yeti memo on display—it was a diplomatic move. The Nepali government had issued the memo two years earlier, but when the U.S. translated it into English, it was signaling its support of Nepal’s sovereign rule. In doing so, the U.S. hoped Nepal—which neighbors China—would be friendly to Americans' desire to keep tabs on China's communist government.

“Although, at first glance, a memo about yeti-hunting seems fanciful, it is in fact representative of American Cold War strategies to combat what they saw as the rising threat of communism,” historian Sanjana Barr writes on the National Archives’ blog.