“And you know that I know that it is true.”

From Susan Easton Black and Larry C. Porter, Martin Harris: Uncompromising Witness of the Book of Mormon (Provo: BYU Studies, 2018), an account of Elder David Dille, an 1842 Nauvoo convert to the Church of Jesus Christ of Latter-day Saints who was now, in 1853, on his way from the Valley of the Great Salt Lake to a mission in England:

It was in the [Edwin] Whiting home [evidently in Kirtland, Ohio] that Martin [Harris] spoke at length of the coming forth of the Book of Mormon — David said they talked the whole day.  Elder Dille asked Martin the direct question, “What do you think of the Book of Mormon?  Is it a divine record?”  Martin’s response was both fervent and insightful as he declared, “I was the right-hand man of Joseph Smith, and I know that he was a Prophet of God.  I know the Book of Mormon is true.”  Then striking his fist on the table, he rejoined — “And you know that I know that it is true.  I know that the plates have been translated by the gift and power of God, for his voice declared it unto us; therefore I know of a surety that the work is true.”  Continuing, he explained, “For did I not at one time hold the plates on my knee an hour-and-a-half, whilst in conversation with Joseph, when we went to bury them in the woods, that the enemy might not obtain them?  Yes, I did.  And as many of the plates as Joseph Smith translated I handled with my hands plate after plate.”  Martin next described the dimensions of the plates, pointing with one of his fingers of his left hand to the back of his right hand and said, “I should think they were so long, or about eight inches, and about so thick, or about four inches; and each of the plates was thicker than the thickest tin.”  (371, italics in the original)

That same evening Elder Dille preached in a house built by Hyrum Smith.  Martin was there, and after they came out of the house, he said to Elder Dille, “Just let me go with you to England, I see you can preach.  You do the preaching and I will bear testimony to the Book of Mormon and we will convert all England.”  (372)