They're also good as portable rock suppliers when building a road. Just put it in a cart that you pull along as you're making it, and take it out to refill, then put it back in and continue building away.
Yeah, I had the same thing happen myself. I wasn't expecting it at all, so I was only able to do a very rough guess-timate based on the fact I'm pretty sure I did two full loads (24+24) and then another 9 stones (for a total of 57).