MLA

MacDonald, George, 1824-1905. Cushman, Charlotte. Box 1, folder 61. 1872 Oct 17. https://collections.library.yale.edu/catalog/16474488.

APA, 6th edition

MacDonald, George, 1824-1905. (["Box 1, folder 61"])(1872 Oct 17)[Cushman, Charlotte]. https://collections.library.yale.edu/catalog/16474488.