Truman Coe says Joseph "deciphered" papyri, this was seen as proof of "divine inspiration."
Truman Coe, Letter to the Editor of the Ohio Observer, in "Mormonism," Cincinnati Journal and Western Luminary, August 25, 1836, [4], in Ohio Observer, August 11, 1836)
Last summer a man came to Kirtland and brought among the Mormons four Egyptian mummies. The exhibition exactly struck their fancy. All the Mormons flocked to see the wonderful sight; and Joseph deciphered some of the hieroglyphics, and made known in writing the name and character and antiquity of some of the mummies;—this was an additional proof of his divine inspiration. The man continued with them a week; and then a command was given them to purchase the whole, which they did for $2400. The mummies were soon sent out for exhibition by one of their apostles, but being unsuccessful, he brought them back to Kirtland, and threw them aside.