Instrument utilized for the transportation of a drawing on a different scale than the original, put into practice between 1603 and 1605 by the German astronomer, Christoph Scheiner and perfected around the middle of the 18th Century by the Parisian tool-maker, Claude Langlois. It consists of four legs of different lengths that are all connected and mobile: on one of these, there is the tracer that should follow the lines of the original design, on another there is a sliding pivot that is adjusted to the desired relationship and that holds a pencil or a pen. Generally, the system is completed by a heavy disk that provides stability to the entire system, however maintaining the mobility of the legs.