MLA

Downie, William, 1819-1893. Diary. Box 1, folder 1. 1859 Sep 10-Sep 20. https://collections.library.yale.edu/catalog/17440590.

APA, 6th edition

Downie, William, 1819-1893. (["Box 1, folder 1"])(1859 Sep 10-Sep 20)[Diary]. https://collections.library.yale.edu/catalog/17440590.