In the seventh instalment of Towards the Tank, David Fletcher describes the potential of the massive Holzschuher from 1558.
This vehicle is believed to be named after Berthold Holzschuher, mayor of Nuremberg in 1551. He became famous for his policies on technology and finance, especially his plan for design of armed vehicles.
This contraption is described as self-moving, although what exactly that means is unclear. It cannot have been mechanically powered in 1558 so one assumes that it was horse or man powered, but it seems to be very large. It evidently carries four cannon on each side plus one at each end and nineteen or twenty musketeers suggesting a crew of 48 at the very least.
As usual it would be confined to firm, level ground if it were able to move at all; quite formidable in the midst of the enemy but totally useless if they moved away. Little is known about it, but it seems to be another example of a machine that looks good on paper but which would be quite useless in real life.