MLA

Mason, William Smith, 1866-. Benjamin Franklin: Epitaph. Box 32, folder 2128. circa 1727. https://collections.library.yale.edu/catalog/2020785.

APA, 6th edition

Mason, William Smith, 1866-. (["Box 32, folder 2128"])(circa 1727)[Benjamin Franklin: Epitaph]. https://collections.library.yale.edu/catalog/2020785.