MLA

Whitman, Walt, 1819-1892. Holograph, corrected. Box 3, folder 115. 1890 Sep 24. https://collections.library.yale.edu/catalog/2053749.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 3, folder 115"])(1890 Sep 24)[Holograph, corrected]. https://collections.library.yale.edu/catalog/2053749.