MLA

Brush, George Jarvis, 1831-1912. Emerson, George H. (2). Box 2, folder 45. 1864. https://collections.library.yale.edu/catalog/32512848.

APA, 6th edition

Brush, George Jarvis, 1831-1912. (["Box 2, folder 45"])(1864)[Emerson, George H. (2)]. https://collections.library.yale.edu/catalog/32512848.