John Boswell describes Joseph as finding spectacles and going from being an idiot to having average intelligence through them.
John L. Boswell, "Mormonism," Supplement to the Connecticut Courant (Hartford, Connecticut) 5, no. 22 (December 15, 1838): 175
On arriving at the place in question, the angel commanded the idiot, whose name was Joe Smith, to take up the stone by the ring. Smith, as well he might, hesitated to comply with such an order, when his companion told him to take it up boldly, for, if he had only 'faith,' God would instantly give him strength to perform the herculean task. Having prayed inwardly for some minutes, Joe took off his coat, and was making preparations for the performance; but the angel reproved him for his want of faith, made him replace his coat upon his shoulders, and that even "if the stone weighed ten thousand tons, divine assistance, through saving faith, would enable him to lift it." Joe became passive in the hands of the angel, grasped the ring, and found, to his astonishment, that the stone weighed as nothing in his hands! On removing it, the idiot discovered that it had served as a covering to a box or chest on the same material, under which were deposited 'twelve golden plates or tables," engraven all over with mystical characters. Upon the upper plate lay a 'pair of spectacles' made of freestone, (save the mark,) which the angel commanded Smith to place astride of his nose. On doing so, Joe's 'tongue was loosened,' as he himself states, and his intellect instantly became like those of other men. He saw through the freestone and the engraving on the golden plates became perfectly intelligible to him. The angel then commanded him to associate with himself 'twelve other men,' whom he named as 'Scribes,' and to interpret to them the writing on the plates.