This is an excerpt from The Joseph Smith Paper, Documents, Vol. 1: July 1828-June 1831.
Notwithstanding their lack of detail, records from Joseph Smith and his scribes demonstrate that he used two separate instruments to translate the Book of Mormon. Smith stated that the first was found with the plates and delivered to him by an angel, who explained it consisted of “two stones in silver bows . . . and that was what constituted seers in ancient or former times and that God had prepared them for the purpose of translating the book.” The text of the Book of Mormon spoke of the same instrument as “interpreters” and foretold that it was to be preserved with the gold plates. By August 1829, Smith apparently referred to this device as “spectacles,” a term he used again in his 1832 history. In January 1833, an article in the church newspaper The Evening and the Morning Star declared that he had translated the Book of Mormon “by the gift and power of God . . . through the aid of a pair of Interpreters, or spectacles—(known, perhaps, in ancient days as Teraphim, or Urim and Thummim).” Soon thereafter Smith apparently began applying the biblical term Urim and Thummim to the interpreters or spectacles.
In addition to the device found with the plates, Joseph Smith also translated using other individual seer stones, which he would place in a hat to limit outside light. He and others apparently later referred to these seer stones as Urim and Thummim, thus making it difficult to determine in later accounts whether they were referring to the device found with the plates or a separate stone that performed the same function. Oliver Cowdery, Smith’s principal scribe for most of the translation, explained, “Day after day I continued, uninterrupted, to write from his mouth, as he translated, with the Urim and Thummim, or, as the Nephites whould have said, ‘Interpreters.’” Joseph Smith’s wife Emma, who also served as a scribe for the translation, described his use of two distinct instruments: “Now the first that my husband translated, was translated by the use of the Urim, and Thummim, and that was the part that Martin Harris lost, after that he used a small stone, not exactly, black, but was rather a dark color.”
Later accounts by Joseph Smith’s close associates—either scribes or other early believers who likely learned of the process from Smith or his scribes—provide some idea of what appeared on the Urim and Thummim or seer stone during the translation process. Joseph Knight Sr., a family friend, recalled that after Smith “put the urim and thummim into his hat and Darkned his Eyes,” a sentence “would apper in Brite Roman Letters then he would tell the writer and he would write it then that would go away the next sentance would Come and so on But if it was not spelt rite it would not go away till it was rite so we see it was marvelous.” Emma Smith reportedly told an interviewer that her husband spelled out difficult or unfamiliar words, including “proper names he could not pronounce.” She further stated, “While I was writing them, if I made any mistake in spelling, he would stop me and correct my spelling, although it was impossible for him to see how I was writing them down at the time. . . . When he stopped for any purpose at any time he would, when he commenced again, begin where he left off without any hesitation.”
Decades after the translation work, David Whitmer, one of the Three Witnesses of the Book of Mormon, wrote that on the “spiritual light” of the seer stone, “a piece of something resembling parchment would appear, and on that appeared the writing. One character at a time would appear, and under it was the interpretation in English. Brother Joseph would read off the English to Oliver Cowdery, who was his principal scribe, and when it was written down and repeated to Brother Joseph to see if it was correct, then it would disappear, and another character with the interpretation would appear. Thus the Book of Mormon was translated by the gift and power of God, and not by any power of man.”
(Dean C. Jessee, Ronald K. Esplin, Richard Lyman Bushman, and Matthew J. Grow, The Joseph Smith Papers, Documents, vol. 1: July 1828–June 1831 [Salt Lake City: The Church Historian’s Press, 2013], xxix–xxxi).