"A Presbyterian" describes the translation as Joseph looking into a small stone and reading the will of the Lord.
"A Presbyterian," Letter, February 22, 1831, Independent Messenger, (Worcester, Massachusetts), 1 no. 24 (June 17, 1831): 96
He [Joseph Smith] has 10 years’ translating to do; he looks in a small stone he has, and there reads the will of the Lord and writes it for the good of his fellow-men; he can read a person’s heart by looking in his face.