Tea Bath?
A) Shallow dish - catches drips from spout, overflow from filling teapot, or holds about enough liquid to let you do one or two 'pour over top of pot' to add more heat to a long brew. This tray is dumped often into the waste water bowl and it isn't primarily meant as a teapot bath. It is more like creating a much more attractive way to contain tea mess than the usual boxy bamboo table.
B) Tea Boat

In cold weather one might actually purposefully create a deeper bath of hot water around a teapot or gaiwan to help maintain temperature.
How much tea?
A lot. Totally depends though, Wuyi tea expands less, fits the pot less densely, and gets a lot more than Taiwanese oolong which expands like crazy. Pictured is Dan Cong, which doesn't expand much, but still gets a lot less leaf than most teas.
Rocks WTF?
http://theteagallery.blogspot.com/2008/ ... r-tea.html
Unfortunately I don't know of anyone importing these right now, best bet is possibly Best Tea House Vancouver branch. It is sort of what some people would call "just a Best Tea House thing." Your mileage may vary.