MLA

Watkins, Carleton E., 1829-1916. Mariposa. Folder 11. [ca. 1860-1861]. https://collections.library.yale.edu/catalog/2017879.

APA, 6th edition

Watkins, Carleton E., 1829-1916. (["Folder 11"])([ca. 1860-1861])[Mariposa]. https://collections.library.yale.edu/catalog/2017879.