MLA
Early, John, 1786-1873. Letter from John Early (Nashville, Tennessee) to Robert Paine (Aberdeen, Mississippi) - October 16, 1860. October 16, 1860. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/508hdr7tv6-cor.
APA, 6th edition
Early, John, 1786-1873. (October 16, 1860)[Letter from John Early (Nashville, Tennessee) to Robert Paine (Aberdeen, Mississippi) - October 16, 1860]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/508hdr7tv6-cor.
Chicago
Early, John, 1786-1873, Letter from John Early (Nashville, Tennessee) to Robert Paine (Aberdeen, Mississippi) - October 16, 1860, October 16, 1860, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/508hdr7tv6-cor.