In his Address to All Believers in Christ, (Richmond, MO: n.p., 1887, 12) David Whitmer wrote:
I will now give you a description of the manner in which the Book of Mormon was translated. Joseph would put the seer stone into a hat, drawing it closely around his face to exclude the light; and in the darkness the spiritual light would shine. 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 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.
According to Edward Stevenson, Martin Harris explained the translation as follows:
By the aid of the seer stone, sentences would appear and were read by the Prophet and written by Martin, and when finished he would say, 'Written,' and if correctly written that sentence would disappear and another appear in its place, but if not written correctly it remained until corrected, so that the translation was just as it was engraven on the plates, precisely in the language then used.