MLA

Whitman, Walt, 1819-1892. Gurney & Son. Box 4, folder 178. 1871. https://collections.library.yale.edu/catalog/2053809.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 4, folder 178"])(1871)[Gurney & Son]. https://collections.library.yale.edu/catalog/2053809.