Despite the Gospel Topics Essay on Translation and the Ensign, there is still at least one page on the Church's site that claims Joseph translated the plates with the Urim and Thummim.
Let's see how long that stays up.
In their Study Edition, the Maxwell Institute put it right after the testimonies of the Three and Eight Witnesses and before Joseph Smith's testimony. The Gospel Topics Essay quotes it, etc.
It seems bizarre that historians give the "Last Testimony" such deference regarding SITH, when they reject what the document says about plural marriage. Emma's son wrote the "Last Testimony" for Emma just a couple of months before she died. She never publicly acknowledged it. It was first published six months after she died. The "Last Testimony" mostly focuses on refuting claims made by Brigham Young and the other "Utah Mormons."
I have an entire chapter about this in my book.
Here's a brief summary of the problem with relying on Emma Smith.
1. She claims Joseph used the Urim and Thummim until the 116 pages were lost, and after that he used the small dark stone. She never saw the Urim and Thummim.
2. She claims she wrote "day after day" as Joseph dictated with his face buried in the hat with the stone in it. This means she translated after the 116 pages were lost.
3. Lucy Mack Smith reported this:
“After the angel left me’, said he [Joseph], “I continued my supplications to God without cessation; and, on the 22d of September , I had the joy and satisfaction of again receiving the Urim and Thummim; and have commenced translating again, and Emma writes for me; but the angel said that the Lord would send me a scribe, and <I> trust his promise will be verified. The angel He also seemed pleased with me, when he gave me back the Urim and Thummim; and he told me that the Lord loved me, for my faithfulness and humility...
4. This is consistent with Emma acting as scribe after the 116 pages were lost, but inconsistent with her claim that he did not use the Urim and Thummim.
Key point: If Emma started writing the translation in the fall of 1828, the common assumption that Joseph translated the plates in 90 days is wrong. Oliver arrived in Harmony in April 1829, seven months after Joseph received back the Urim and Thummim and began translating.
We assume that, after the 116 pages were lost, Joseph began translating the Book of Mosiah. The original manuscript for the Book of Mosiah was ruined so we don't know who the scribe was. [The surviving portion of the original manuscript starts with Alma 22.]
Oliver Cowdery said he wrote the entire original manuscript, "save a few pages only." We have the original manuscript for most of 1 Nephi and part of 2 Nephi, which were written in Fayette. Several chapters of 1 Nephi were written by John Whitmer and another scribe (probably Christian Whitmer). These "few pages" align with what Oliver said.
If Emma really wrote "day after day" and she was writing Joseph's translation of the plates after the 116 pages were lost, then there are three possibilities:
1. she wrote much of the Book of Mosiah (and maybe Alma) before Oliver arrived in April;
2. she wrote something else;
3. she misremembered, conflated accounts, or was misquoted.
These are some of the issues I address in the chapter in the book.