MLA

Eliot, George, 1819-1880. Letter. Box 7. 1885 Jan 27. https://collections.library.yale.edu/catalog/10001239.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 7"])(1885 Jan 27)[Letter]. https://collections.library.yale.edu/catalog/10001239.