Notes: "The Hounsfield Planimeter solves one of the problems with most hatchet planimeters: keeping it perfectly upright. The large circular frame around the tracing point rides on the paper, stabilizing the planimeter. The u-joint connecting the tracing point to the beam ensures that any unevenness in the paper is not transmitted back to the hatchet blade. There is also a lancet-like blade that can be pushed into the paper at the start and end of the measurement, making measuring the distance between those points easier."
