This picture shows an early (14th century?) example of a 6-pulse rectifier. Note the trip hammers 'D' and 'E' for pounding paper pulp. They are operated by toggles 'C', spaced in phase around shaft 'B'. The drawing is full of artistic errors: there are 6 toggles and hammers, but the number of sides on the shaft are not an integral multiple of 6; the mule is hunchback rather than swayback (but maybe mules are like this); all three men are looking over their shoulders; the screw thread for the press is reversed, or the man is pulling the wrong way; the blocking plate at 'F' should be on the underside of the crosspiece, not on top; etc. etc.