MLA

Wharton, Edith, 1862-1937. Mitchell, S. Weir. Box 61, folder 1740. [1902]. https://collections.library.yale.edu/catalog/17111186.

APA, 6th edition

Wharton, Edith, 1862-1937. (["Box 61, folder 1740"])([1902])[Mitchell, S. Weir]. https://collections.library.yale.edu/catalog/17111186.