Callimachus, referred to by historians as Callimachus of Cyrene was a noted poet, critic and scholar at the Library of Alexandria.
Although he was never made chief librarian, Callimachus was responsible for producing a bibliographic survey based upon the contents of the Library, and was best known for his short poems and epigrams.
Around 250 BC, Callimachus wrote a text (that later bore the title of Callimachus text) which noted the locations of the seven Pieces of the Golden Capstone, which Alexander the Great had arranged to be hidden by priests of the Cult of Amun Ra within constructs that would become known as the seven Wonders of the Ancient World.
Callimachus wrote the text in the Word of Thoth, a mysterious language that few people could read or write (presumably he had been taught by the Oracle of Siwa or someone else who knew the language), to make it difficult for any unlearned person to uncover should they only be seeking the Capstone Pieces for selfish means.
After Callimachus died around 240 BC, his fellow scholars in the Library of Alexandria would keep the text safe within the Library, however in 48 BC, when the Library of Alexandria was in imminent danger of being burned down, one of the librarians managed to spirit away a number of scrolls to another location, including the Callimachus text.