[klyrs]

> How does one carve the interior cavity of an urn with the most rudimentary of tools?

Abrasive grit. You can make a saw out of a plank with grit -- the grit will eat the plank faster than stone, but it can cut through granite because quartz in the sand is harder than granite. Similarly, you can make a drill with a dowel and grit. The step from drill to lathe is pretty obvious to me.

And don't forget time. People with primitive technology have an astounding amount of patience compared to soft-handed technologists. Speaking as a soft-handed technologist, of course.