MLA
Scarborough, R. P. Letter from R. P. Scarborough (Manassas, Virginia) to His Cousin, Araminta Williams - December 31, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 13. https://digital.library.emory.edu/purl/576rxwdchp-cor.
APA, 6th edition
Scarborough, R. P. (1861). Letter from R. P. Scarborough (Manassas, Virginia) to his cousin, Araminta Williams - December 31, 1861 (Box 6, Folder 13) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/576rxwdchp-cor.
Chicago
Scarborough, R. P. “Letter from R. P. Scarborough (Manassas, Virginia) to His Cousin, Araminta Williams - December 31, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 6, Folder 13. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/576rxwdchp-cor.