MLA

Emerson, Ralph Waldo, 1803-1882. Carlyle, Thomas. Box 1, folder 33. 1862 May 10. https://collections.library.yale.edu/catalog/2067826.

APA, 6th edition

Emerson, Ralph Waldo, 1803-1882. (["Box 1, folder 33"])(1862 May 10)[Carlyle, Thomas]. https://collections.library.yale.edu/catalog/2067826.