A 1983 German postage stamp commemorating the Reinheitsgebot.
So perhaps a bit off topic, but any good beer drinker knows about the Reinheitsgebot. So, 500 years ago - in April 1516 - the Duke of Bavaria laid down the law by issuing an edict dictating just what ingredients could go in beer, namely: water, barely and hops. Sorry, but no yeast. But then again nobody knew about yeast 500 years ago. The new law was called the Reinheitsgebot, say: Rine-Hites-ge-Boat. Some beer historians theorize that the good Duke really didn't care all that much about the purity of beer, but rather he wanted to control the various grain supplies.
The Reinheitsgebot is still in force, but not enforced, today, and many German brewers are now doing their own thing. Regardless, many a German beer purist will insist his or her beer is made to the letter of the Reinheitsgebot law. Indeed, many German brewers proudly proclaim their adherence to the law. Cheers, or more accurately, Prost!