Because of the Saints book, a lot of people in the Church are focusing on the question of the Hill Cumorah.
Elizabeth Kane and her husband, General Thomas Kane, were not members of the Church, but they were very friendly to Brigham Young. Gen. Kane helped negotiate peace in the Utah War.
The Kanes were invited to St. George for a couple of months in 1872. Elizabeth wrote a memoir of her time in St. George, Utah, from 1872-3 that included a conversation with Brigham Young and others about the Hill Cumorah.
In this account, she relates how Brigham Young told her that when Joseph and Oliver entered the repository the third time, their eyes adjusted to the dim light so they could see all the artifacts.
You can read the typed manuscript here.
Key passages are found on pages 74-5.
It's also interesting that when she asked where Cumorah was, she was told "in Manchester Township, Ontario County, New York."