Notes: "Like the disc planimeters, the spherical planimeter exists to improve accuracy. But rather than have a better paper for the wheel to roll on, the paper and tracing wheel are entirely replaced by a roller and spherical surface, each with a finely ground finish that eliminates any slippage. The sphere is driven by the planimeter's wheels, and the angle of the tracing arm determines which part of the sphere that the cylindrical roller contacts. This planimeter appears to be identical to the K&E model 4262 shown in the 1913 K&E catalog."
