MLA
Easton, Laura M. Letter from Laura M. Easton[?] to "My Dear Sister" - May 27, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 62. https://digital.library.emory.edu/purl/699n2z35x2-cor.
APA, 6th edition
Easton, L. M. (1861). Letter from Laura M. Easton[?] to "My Dear Sister" - May 27, 1861 (Box 5, Folder 62) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35x2-cor.
Chicago
Easton, Laura M.[?]. “Letter from Laura M. Easton[?] to ‘My Dear Sister’ - May 27, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 5, Folder 62. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35x2-cor.