From Dard Hunter [American Arts and Crafts-era designer and papermaker, who began his career initially as a chalk talk lecturer], My Life with Paper: An Autobiography. NY: Alfred A. Knopf, 1958, p. 24—
[In 1900, after Hunter had painstakingly prepared the apparatus for a Chautauqua chalk talk, his set-up was accidentally undone by the famous orator William Jennings Bryan, who clumsily entangled himself in the wires as he entered to stage for a lecture. When Bryan did not apologize, recalls Hunter,) I was aching for revenge…With my pocket knife I grated an entire piece of soft red chalk into the inside of Bryan's headpiece. It was a hot morning, and after the lecture Bryan placed the great broad hat on his perspiring head. The finely powdered red chalk mingled with the perspiration, and the classical face of William Jennings Bryan was literally streaked with bright-red pigment as he walked to his hotel.