John Muir’s Desk Clock (Madison, WI)
Image by vige
John Muir created this contraption to regulate the time he spent studying any individual book. A letter describes its function: "It gave him a prescribed time to study a lesson and then revolved, bringing into place the next book. My mother who had a keen sense of humor, told him the invention did not go far enough; that he ought to have so arranged it that if he hadn’t properly learned the lesson, a hand would come up and box his ears." (Wisconsin Historical Society)