MLA

Ely, William Davis, 1815-1908. Budington, William Ives. Box 1, folder 3. 1839. https://collections.library.yale.edu/catalog/32532120.

APA, 6th edition

Ely, William Davis, 1815-1908. (["Box 1, folder 3"])(1839)[Budington, William Ives]. https://collections.library.yale.edu/catalog/32532120.