Mary Whitmer
Mary Whitmer (mother of David Whitmer) saw the plates at her farm in Fayette, New York, when a divine messenger she identified as "Brother Nephi" showed them to her. This messenger, whom Joseph Smith had previously identified as one of the Three Nephites, picked up the abridged plates from Joseph in Harmony, Pennsylvania. He met Joseph, Oliver and David Whitmer on their trip from Harmony to Fayette. He told them he was going to Cumorah. Later, he brought the plates of Nephi to Fayette so Joseph could translate them there. That's when he showed the plates to Mary, presumably to reassure her that the translation work was important despite the extra burdens Mary assumed by feeding and housing Joseph and Oliver.
There are several accounts of Mary's experience. Her grandson said that although Mary identified the messenger as "Brother Nephi," she must have been mistaken because (in his opinion) it must have been Moroni. This has led to confusion about the identity of the messenger, but David Whitmer clarified that Joseph Smith identified the messenger as one of the Three Nephites. David related his conversations with both the messenger and Moroni and knew they were different people.
This makes sense because the messenger was a heavy-set, short, older man. Moroni was a resurrected person who was taller than average. There is no doctrinal or logical reason why a resurrected being would be able to change his body size, age, and appearance.
Original Sources.
One original source for the Mary Whitmer witness of the plates is the interview of David Whitmer by Joseph F. Smith and Orson Pratt (see the link here: https://www.mobom.org/resources-fayette-trip). They asked David to describe the messenger, which he did. Shortly prior to that question, though, they asked David if he really saw the angel who showed him the plates. He affirmed that he did, that the angel stood just a few feet away, etc. Oddly, they didn't ask David to describe the angel, or if they did they didn't mention it in their account. But David clearly distinguished between the angel and the messenger because they were not the same person.
In 1884, B.H. Roberts interviewed David Whitmer. Here's one account he related in General Conference, October 1926:
Shortly after breakfast the four named went out into the woods, as I have said, and there supplicated the Lord with the result that they beheld the plates and the engravings thereon, and they heard the voice of God proclaim that the translation was true and he commanded them to bear witness of it to all the world.
In my interview with David Whitmer, in 1884, as he went over this ground, led by my questions, when we came to this part of it he said to me that in the progress of turning the leaves, or having them turned by Moroni, and looking upon the engravings, Moroni looked directly at him and said: “David, blessed is he that endureth to the end.” When David Whitmer made that remark it seemed to me rather a peculiar thing that he should thus be singled out for such a remark, and I remember reporting it as such to President John Morgan, then president of the Southern States mission. I stated to him the peculiar feelings I had when I learned that from the lips of David Whitmer; but the subsequent history of these three witnesses led me to conclude that there was indeed a hidden warning in the words of the angel to David, “Blessed is he that endureth to the end.” And it is rather a sad reflection that of these three witnesses he was the only one who died outside of membership in the Church. I wonder if Moroni was not trying to sound a warning to this stubborn man, that perhaps whatever his experiences and trials might be, that at the last he, too, might have been brought into the fold, and might have died within the pale of the Church.
David's encounter with Moroni occurred in June 1829, within a month of his encounter with the messenger who was taking the abridged plates to Cumorah. Certainly, when asked about the messenger, David would not forget to explain that the messenger was the same person who showed David the plates.
Instead, he described the messenger's appearance as someone entirely different from Moroni.
David apparently related the incident as early as 1832, when he and Hyrum Smiths were missionary companions who baptized the family of Zina D. H. Young. Years later, Zina asked Edward Stevenson, who was leaving on a trip to interview David Whitmer, to ask David about the messenger.
In his journal, Edward Stevenson related David's statement that Joseph identified the messenger as one of the Nephites:
"I wish to mention an Item of conversation with David Whitmer in regard to Seeing one of the Nephites, Zina Young, Desired me to ask about it. David Said, Oliver, & The Prophet, & I were riding in a wagon, & an aged man about 5 feet 10, heavey Set & on his back, an old fashioned Armey knapsack Straped over his Shoulders & Something Square in it, & he walked alongside of the Wagon & Wiped the Sweat off his face, Smileing very Pleasant David asked him to ride and he replied I am going across to the hill Cumorah. Soon after they Passed they felt Strangeley and Stoped, but could see nothing of him all around was clean and they asked the Lord about it. He Said that the Prophet Looked as White as a Sheet & Said that it was one of the Nephites & that he had the plates."
Link to the original source: http://contentdm.lib.byu.edu/cdm/ref/collection/BYUIBooks/id/3527
You can find this account in these references, although apparently not transcribed exactly: "Edward Stevenson Interview (1) 22-23 December 1877, Richmond, Missouri Diary of Edward Stevenson," LDS Church Archives, Lyndon W. Cook, ed., David Whitmer Interviews, 1993, p. 13; also Dan Vogel, ed., Early Mormon Documents, 2003, vol. v, p. 30.
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We have no record of Joseph or Oliver describing the messenger, although we do have multiple accounts of Oliver and Joseph visiting the repository of Nephite records in the Hill Cumorah--the destination of the messenger.
What we do have is Oliver's description of Moroni in Letter IV, which he wrote with the assistance of Joseph and which Joseph made sure was republished several times so all the Saints could learn about Moroni's visit. Oliver wrote, "The stature of this personage was a little above the common size of men in this age; his garment was perfectly white, and had the appearance of being without seam."
We also have the original version of Joseph Smith--History 1:33, published in the Times and Seasons in 1842, which identified the angel as Nephi. That reference (which was compiled by Joseph's scribes, not written by Joseph in the first place) was later changed to Moroni, and Brigham Young explained that both Nephi and Moroni ministered to Joseph. They were not one individual in two different bodies. One was resurrected. The other was changed so he wouldn't taste death, as we learn in 3 Nephi 28 (see below).
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Some of the confusion about the identity of the messenger arose from a page from the Historical Record cited by Saints as authority for the Moroni claim. Here's the link:
Here's the image of the page from the Historical Record.
Everyone can see that Mary herself "always called" the messenger, or holy angel, "Brother Nephi."
It was her grandson who unilaterally decided "she undoubtedly refers to Moroni, the angel who had the plates in charge."
Mary's identification makes sense historically and doctrinally, while her grandson's "correction" is purely his own theory.
It makes sense that Mary "always called" the messenger "Brother Nephi" because Nephi was the name of one of the disciples from whom the group of three were granted their desire to never taste of death.
1 And it came to pass when Jesus had said these words, he spake unto his disciples, one by one, saying unto them: What is it that ye desire of me, after that I am gone to the Father?
2 And they all spake, save it were three, saying: We desire that after we have lived unto the age of man, that our ministry, wherein thou hast called us, may have an end, that we may speedily come unto thee in thy kingdom.
3 And he said unto them: Blessed are ye because ye desired this thing of me; therefore, after that ye are seventy and two years old ye shall come unto me in my kingdom; and with me ye shall find rest.
4 And when he had spoken unto them, he turned himself unto the three, and said unto them: What will ye that I should do unto you, when I am gone unto the Father?
5 And they sorrowed in their hearts, for they durst not speak unto him the thing which they desired.
6 And he said unto them: Behold, I know your thoughts, and ye have desired the thing which John, my beloved, who was with me in my ministry, before that I was lifted up by the Jews, desired of me.
7 Therefore, more blessed are ye, for ye shall never taste of death; but ye shall live to behold all the doings of the Father unto the children of men, even until all things shall be fulfilled according to the will of the Father, when I shall come in my glory with the powers of heaven.
8 And ye shall never endure the pains of death; but when I shall come in my glory ye shall be changed in the twinkling of an eye from mortality to immortality; and then shall ye be blessed in the kingdom of my Father.
9 And again, ye shall not have pain while ye shall dwell in the flesh, neither sorrow save it be for the sins of the world; and all this will I do because of the thing which ye have desired of me, for ye have desired that ye might bring the souls of men unto me, while the world shall stand.
(3 Nephi 28:1–9)
We also assume that the Three Nephites were the three men who prepared David's fields so he could go pick up Joseph and Oliver from Harmony.
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