MLA
Boring, Jesse. Letter from Jesse Boring (San Francisco, California) to Robert Paine (Aberdeen, Mississippi) - May 2, 1853. 1853. Pitts Theology Library, Box 1, Folder 4. https://digital.library.emory.edu/purl/948sbcc3n9-cor.
APA, 6th edition
Boring, J. (1853). Letter from Jesse Boring (San Francisco, California) to Robert Paine (Aberdeen, Mississippi) - May 2, 1853 (Box 1, Folder 4) [Letters (correspondence)]. Pitts Theology Library. https://digital.library.emory.edu/purl/948sbcc3n9-cor.
Chicago
Boring, Jesse. “Letter from Jesse Boring (San Francisco, California) to Robert Paine (Aberdeen, Mississippi) - May 2, 1853.” Letters (correspondence). Robert Paine Papers, 1828-1882, 1853. Box 1, Folder 4. Pitts Theology Library. https://digital.library.emory.edu/purl/948sbcc3n9-cor.