MLA

Whitman, Walt, 1819-1892. Unidentified. Box 11, folder 239. n.d.. https://collections.library.yale.edu/catalog/2053862.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 11, folder 239"])(n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2053862.