I
recently learned a great deal about the history of how ornamentation in architecture has been produced, thanks to this fascinating article here. In particular, the device known as a Pointing Machine is a remarkable piece of technology from the late middle ages into the twentieth century.
Basically, marble statues are, almost as a rule, not "originals" in the process of creation. Rather, artists typically made their sculptures in the much-easier-to-work clay, then cast the clay sculpture in plaster for longevity (as clay cracks and breaks as it dries). This plaster cast is then hooked up to an apparatus that enables the transfer of points in three-dimensional space from the plaster to the block of marble. This point-transferral is repeated thousands of times, typically by a regular craftsman who had no hand in the original sculpture's design. What is produced is a remarkably accurate copy of the original clay, but now in stone, and able to be replicated at some measure of scale by a fleet of less-talented workers. I highly recommend looking up videos of Pointing Machines in use, they are fascinating.