CLEMENS, SAMUEL ("Mark Twain"). Autograph letter signed ("S.L. Clemens") to the sculptress, Mrs. Bettina Wirth, regarding sitting for a bust portrait to be done by Wirth. N.p., 28 October 1897. 2 pages, small 8vo, on black-boredered staionery, minor wear at folds. "... I am now as always, yours to command; & so, I am ready to sit for that bust, beginning next Tuesday or any day thereafter..." With a 4-line postscript at end.