MLA

Eliot, George, 1819-1880. Appleton, Charles Edward Cutts Birch. Box 5. [1871 Feb 6]. https://collections.library.yale.edu/catalog/17468799.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 5"])([1871 Feb 6])[Appleton, Charles Edward Cutts Birch]. https://collections.library.yale.edu/catalog/17468799.