Even in Kyoto

This is pretty much useless advice, I know, but I've done a lot of hole drilling using old ship augers. They're useless here, and if they're too worn to be resharpened, using them to punch holes in dirt isn't really a waste. I have one that's a meter long, and boy does it do a great job of putting a nice 22mm hole down through the ground. It wouldn't handle a football-sized rock, but it'll push aside fist-sized rocks on its way down. I've seen some others at a local scrapyard that must be two meters long. No idea how I'd drive them, but http://www.irwin.com/tools/drill-bits/ship-auger-bits. (Mine have a tapered square shank for use with wood braces, rather than these intended for power drills, because mine are probably 120 years old.)