MLA
Boring, Jesse. Letter from Jesse Boring (San Francisco, California) to Robert Paine - September 8, 1852. 1852. Pitts Theology Library, Box 1, Folder 4. https://digital.library.emory.edu/purl/259c59zx92-cor.
APA, 6th edition
Boring, J. (1852). Letter from Jesse Boring (San Francisco, California) to Robert Paine - September 8, 1852 (Box 1, Folder 4) [Letters (correspondence)]. Pitts Theology Library. https://digital.library.emory.edu/purl/259c59zx92-cor.
Chicago
Boring, Jesse. “Letter from Jesse Boring (San Francisco, California) to Robert Paine - September 8, 1852.” Letters (correspondence). Robert Paine Papers, 1828-1882, 1852. Box 1, Folder 4. Pitts Theology Library. https://digital.library.emory.edu/purl/259c59zx92-cor.