Thomas Hamilton said that Joseph used the spectacles to translate the BOM.

In this emergency, Smith judged it more prudent to shoulder his spade, than by farther obstinacy to excite the vengeance of some unearthly intelligence. Having dug to the requisite depth in the place commanded, he found a book with golden clasps and cover, and a pair of elegantly mounted spectacles, somewhat old-fashioned to be sure, but astonishing magnifiers, and possessing qualities which it might puzzle Sir David Brewster to explain on optical principles. Smith had some difficulty in undoing the clasps of this precious volume, but on opening it, though his eyes were good, it appeared to contain nothing but blank paper. It then occurred to him to fit on his spectacles, when, lo! the whole volume was filled with certain figure and pot-hooks to him unintelligible. Delighted with his good fortune, Smith trudged home with the volume in his pocket and the spectacles on his nose, happy as bibliomaniac who has been lucky enough to purchase some rare Editio Princeps "dog cheap" from the ignorant proprietor of an obscure book-stall. On reaching his own house, his first care was to secure his miraculous treasures from profane observation; his second, to copy out a page or two of the characters, and look about for an interpreter. His search was long fruitless, but, at length, he hit on precisely the two individuals who were qualified conjointly for the office. One of these gentlemen possessed the faculty of reading the hieroglyphics, and the other of interpreting them. See Full