Lucy Mack Smith describes Joseph being told about the ancient Nephites by Moroni.
Lucy Mack Smith, History, 1844–1845, 1–2, bk. 4, Joseph Smith Papers
In the course of our evening conversations Joseph would give us some of the most ammusing recitals which could be immagined he would de[s]cribe the ancient inhabitants of this continent their dress thier maner of traveling the animals which they rode The cities that were built by them the structure of their buildings with every particular of their mode of warfare their religious worship as particularly as though he had Spent his life with them it will be recollected by the reader that all that I mentioned and much more took place within the compass of one short year