MLA

Whitman, Walt, 1819-1892. Holograph manuscript. Box 3, folder 145. n.d.. https://collections.library.yale.edu/catalog/2001528.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 3, folder 145"])(n.d.)[Holograph manuscript]. https://collections.library.yale.edu/catalog/2001528.