MLA

Eliot, George, 1819-1880. Letter. Box 10. 1902 Jul 23. https://collections.library.yale.edu/catalog/32365695.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 10"])(1902 Jul 23)[Letter]. https://collections.library.yale.edu/catalog/32365695.