MLA

Eliot, George, 1819-1880. Letter. Box 9. 1885 Mar 26. https://collections.library.yale.edu/catalog/32368884.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 9"])(1885 Mar 26)[Letter]. https://collections.library.yale.edu/catalog/32368884.