The Bavarian Purity Law
The Purity Law is the last chapter of a protracted development of resolutions, lasting over 200 years, in order to regulate the brewing of beer so that neither unhealthy adjunctions nor grain (substantial for bread production) were used. Furthermore it determined all prices related to beer and thereby further secured the two basic foodstuffs of Bavarian people, bread and beer.
In the course of centuries this brewing regulation has gradually been acknowledged by all German countries and, since 1906, by the whole First German Empire and its successors until modern Germany. Yet the German Beer Law is based on the Bavarian Purity Law, which is as well and nonetheless an indication of outstanding quality.
Translation from German of the "Reinheitsgebot".
How beer is to be brewed and poured out across the land:
[…]We decree, establish and ordain at the behest of the Lords of Bavaria that henceforth in all the land, in the countryside as well as our towns and marketplaces, there is no other policy than this: From Michaelmas until the Feast of St George, one mug(1) or 'head'(2) of beer will not be sold for more than one Munich penny; and from the Feast of St George until Michaelmas, a mug will not be sold for more than two pennies of the same reckoning, and a head for no more than three heller(3), under pain of penalty. But when one brews any beer (other than Marzenbier), it will under no circumstances be poured or sold for more than one penny per mug. Further we decree that henceforth in all our towns, marketplaces and the whole of the countryside, no beer shall contain or be brewed with more ingredients than grain, hops, and water. He who knowingly violates these laws will be summarily fined every kegs of such beer each time it happens.
(1) Mug = (Bavarian) 1.069 Liters
(2) Head = round container for fluids, containing slightly less than one Bavarian 'mug'
(3) Heller = Munich half-penny