MLA

Kern, Edward Meyer, 1823-1863. "In San Miguel - Light[?]" Pencil drawing. Box 2, folder 20. n.d.. https://collections.library.yale.edu/catalog/10000691.

APA, 6th edition

Kern, Edward Meyer, 1823-1863. (["Box 2, folder 20"])(n.d.)["In San Miguel - Light[?]" Pencil drawing]. https://collections.library.yale.edu/catalog/10000691.