MLA
Capers, William, 1790-1855. Letter from William Capers (Charleston, South Carolina) to Robert Paine (Aberdeen, Mississippi) - March 15, 1847. March 15, 1847. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/26663xsk8q-cor.
APA, 6th edition
Capers, William, 1790-1855. (March 15, 1847)[Letter from William Capers (Charleston, South Carolina) to Robert Paine (Aberdeen, Mississippi) - March 15, 1847]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/26663xsk8q-cor.
Chicago
Capers, William, 1790-1855, Letter from William Capers (Charleston, South Carolina) to Robert Paine (Aberdeen, Mississippi) - March 15, 1847, March 15, 1847, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/26663xsk8q-cor.