scroll-plate

from The Century Dictionary.

• noun In experimental psychology, an apparatus used to test steadiness of motor coördination. A glass plate is covered with a sheet of tin-foil, in which a narrow and complicated scroll pattern has been cut. The subject is given a tracing needle, and is required to follow out the pattern without touching the tin-foil. Electrical connections are so made that, for instance, a bell rings every time that the needle leaves the middle of the slit and comes into contact with its edge.