George Q. Cannon cites David Whitmer reporting that Joseph translated with a stone in the hat "which all light was excluded."
George Q. Cannon, Journal entry for February 27, 1884, Church Historians Press, accessed August 30, 2021
In speaking of the translating he [David Whitmer] said that Joseph had the stone in a hat which all light was excluded. In the stone the characters appeared and under that the translation in English and they remained until the scribe had copied it correctly. If he had made a mistake the words still remain and were not replaced by any other.