David Whitmer tells J.L. Traughber that Joseph used a seer stone in the translation of the Book of Mormon; U&T narrative was introduced later.
J.L. Traughber Jr., "Testimony of David Whitmer," Saints' Herald 26, no. 22 (November 15, 1879): 341, M291.5 S157 v. 1- 1860-, Church History Library
I, too, have seen the "manuscripts" and examined them. I, too, have heard Father [David] Whitmer say that he was present many times while Joseph was translating, but I never heard him say that the translation was made by aid of Urim and Thummim; but in every case, and his testimony is always the same, he declared that Joseph first offered prayer, then took a dark colored, opaque stone, called a "seer-stone," and placed it in the crown of his hat, then put his face into the hat, and read the translation as it appeared before him. This was the daily method of procedure, as I have often heard Father Whitmer declare; and, as it is generally agreed to by parties who know the facts, that a considerable portion of the work of translation was performed in a room of his father's house, where he then resided, there can be no doubt but what Father David Whitmer is a competent witness of the manner of translating . . . With the sanction of David Whitmer, and by his authority, I now state that he does not say that Joseph Smith ever translated in his presence by aid of Urim and Thummim; but by means of one dark colored opaque stone, called a "Seer Stone," which was placed in the crown of a hat, into which Joseph put his face, so as to exclude the external light. Then a spiritual light would shine forth, and parchment would appear before Joseph, upon which was a line of characters from the plates, and under it, the translation in English; at least so Joseph said.