Boston Investigator reports that Joseph used the Urim and Thummim, two crystal stones, to translate the BOM.
“Questions proposed to the Mormonite Preachers and their answers obtained before the whole assembly at Julian Hall, Sunday Evening, August 5, 1832,” Boston Investigator 2, August 10, 1832
Q. — By what means did he discover the golden plates and who was with him when he made the discovery? A. — The golden plates were discovered through the ministration of an angel of the Lord, by Joseph Smith — no one else was with him at the time of the discovery. Q. — By whom was a fac simile of some part of the language and characters taken, and on what material. A. — It was taken by Joseph Smith on paper from the original plates themselves. Q. — By whom was this presented to Dr. Mitchell, and at what period? A. — By Martin Harris, one of the witnesses who had seen the plates — do not exactly know at what time. Q. — Is that fac simile, now in being, and if so where is it? A. — It is, or it was in being — I have seen it. Q. — In what manner was the interpretation, or translation made known, and by whom was it written? A. — It was made known by the spirit of the Lord through the medium of the Urim and Thummim; and was written partly by Oliver Cowdery, and partly by Martin Harris. Q. — What do you mean by Urim and Thummim? A. — The same as were used by the prophets of old, which were two crystal stones, placed in bows, something in the form of spectacles, which were found with the plates. Q. — What became of the plates after the translation was made? A. — They were delivered into the hands of the angel of the Lord by whom they were afterwards shown to the three witnesses, who have testified to that effect. Q. — At what place was the translation made? A. — Partly at Manchester, Ontario county, N. Y. where the plates were found, and partly on the banks of the Susquehannah river in Pennsylvania.