MLA

Watkins, Carleton E., 1829-1916. [Two unidentified children, view from above, standing ankle-deep in a body of water]. Folder 28. [ca. 1860-1861]. https://collections.library.yale.edu/catalog/2017981.

APA, 6th edition

Watkins, Carleton E., 1829-1916. (["Folder 28"])([ca. 1860-1861])[[Two unidentified children, view from above, standing ankle-deep in a body of water]]. https://collections.library.yale.edu/catalog/2017981.