Broken pottery shards must have been really common as the ancient Athenians used them (ostrakons) to vote with. they would scratch their vote on the shard and drop it in the box.
Sounds a lot more trustworthy than voting machines.
Those clay vessels were also chamber pots-I read in a textbook years ago that those potshards were also used to denounce those who had done something outrageous/scandalous by scratching the name of the perpetrator on a bunch of shards and dumping them on his/her doorstep in the dead of night-the symbolism being that person is being shunned/not fit to be pissed on...
Apparently, clay pots were the aluminum cans, wine bottles, Tupperware and toilet fixtures of the day.