MLA

Boswell, James, 1740-1795. Sasine. Box 79, folder 1550. 1504. https://collections.library.yale.edu/catalog/16030387.

APA, 6th edition

Boswell, James, 1740-1795. (["Box 79, folder 1550"])(1504)[Sasine]. https://collections.library.yale.edu/catalog/16030387.