MLA
Hunter, R. M. T. (Robert Mercer Taliaferro), 1809-1887. Letter from Robert Mercer Taliaferro Hunter to Robert Tyler - April 16, [no year provided]. April 16, year unknown. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/774qjq2cw1-cor.
APA, 6th edition
Hunter, R. M. T. (Robert Mercer Taliaferro), 1809-1887. (April 16, year unknown)[Letter from Robert Mercer Taliaferro Hunter to Robert Tyler - April 16, [no year provided]]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/774qjq2cw1-cor.
Chicago
Hunter, R. M. T. (Robert Mercer Taliaferro), 1809-1887, Letter from Robert Mercer Taliaferro Hunter to Robert Tyler - April 16, [no year provided], April 16, year unknown, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/774qjq2cw1-cor.