Theodore Farley in 1940 recounts Martin Harris affirming testimony in the Book of Mormon having been translated by the gift and power of God.
Talk given by Theodore Farley, Sr., at Priesthood Session of Sharon Stake Quarterly Conference, March 23, 1940, 1-2 in John W. Welch, "Documents of the Translation of the Book of Mormon" in John W. Welch, ed., Opening the Heavens: Accounts of Divine Manifestations, 1820-1844, 2nd ed. (Provo, UT: BYU Studies, 2011), 156
[A]fter the angel had shown him the plates and disappeared, he [Martin Harris] heard a voice from Heaven that thrilled every fiber of his body, stating that the book had been translated by the gift and power of God, and not of man, and he was commanded by the Lord to so make that statement to the world. And he did.
needs a scan Church History Library Call Number MS 4897 (reproduced in Vogel, EMD 2:391); will get scan 07/06