In 1912 Wilfrid Voynich, a Polish-Lithuanian book dealer, bought a book that he could not sell. After his death, his wife could not sell it. After her death it passed to another dealer who couldn’t sell it. The writing was indecipherable so no one knew what it was they were being asked to buy. Eventually it was donated to Yale University.
For a long time many scholars suspected it was a forgery, but recent scientific research has dated the Voynich manuscript to around 600 years old.
It still baffles cryptographers today. In addition to its unknown language, it features numerous beautiful illustrations of mysterious plants, that have yet to be identified. Check out Lisa Fagin Davis’s thread to know more!