MLA

Emerson, Ralph Waldo, 1803-1882. Research notes. Box 1, folder 35. undated. https://collections.library.yale.edu/catalog/17359872.

APA, 6th edition

Emerson, Ralph Waldo, 1803-1882. (["Box 1, folder 35"])(undated)[Research notes]. https://collections.library.yale.edu/catalog/17359872.