Martin Harris tells Simon Smith that Joseph the Urim and Thummim to translate the BOM.
Simon Smith to the editor, April 30, 1884, Saints’ Herald 31, no. 21 (May 24, 1884): 324, M291.5 S157 v. 1- 1860-, Church History Library
He [Martin Harris] also said, “I was Joseph Smith’s scribe, and wrote for him a great deal; for he was such a poor writer, and could not even draw up a note of hand as his education was so limited. I also wrote for him about one third of the first part of the translation of the plates as he interpreted them by the Urim and Thummim. And I paid the printer about three thousand dollars for the first edition of the Book of Mormon.”