MLA
Wightman, William M. (William May), 1808-1882. Letter from William M. Wightman (Charleston, South Carolina) to Robert Paine - July 26, 1849. July 26, 1849. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/921ghx3gk9-cor.
APA, 6th edition
Wightman, William M. (William May), 1808-1882. (July 26, 1849)[Letter from William M. Wightman (Charleston, South Carolina) to Robert Paine - July 26, 1849]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/921ghx3gk9-cor.
Chicago
Wightman, William M. (William May), 1808-1882, Letter from William M. Wightman (Charleston, South Carolina) to Robert Paine - July 26, 1849, July 26, 1849, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/921ghx3gk9-cor.