MLA

Whitman, Walt, 1819-1892. Conway, Moncure D.[aniel]. Box 2, folder 63. 1887 Mar 19. https://collections.library.yale.edu/catalog/2053697.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 2, folder 63"])(1887 Mar 19)[Conway, Moncure D.[aniel]]. https://collections.library.yale.edu/catalog/2053697.