Joseph Smith completes 116 pages (foolscap-size) of translation from the gold plates (the book of Lehi), with Martin Harris transcribing with a blanket stretched between them. Martin Harris repeatedly asks Joseph Smith to borrow the transcript. Smith refuses twice but relents (by revelation) on the third request but makes Harris agree to a covenant to show only his family. Harris brings the 116 page translation from the gold plates back to Palmyra and shows them to his wife, Lucy Harris, but he loses the transcripts (says they were stolen). Lucy Harris is suspected of hiding or destroying them.
[Source: On This Day in Mormon History, http://onthisdayinmormonhistory.blogspot.com]