There was a law against brewing with oats, wheat, rye and dinkel put forth in the fee imperial city of Nurnberg in 1290. Barley was the only cereal grain allowed for brewing beer. At times, this law is drawn on to be the oldest Purity Law in error. Actually the reason for the law was to assure that valuable bread cereals would be used for beer brewing.
The actual Purity Law is a result of the Bavarian Duke, Wilhelm IV. He instated the law at the Ingolstadt Parliament in 1516. The reason to institute such a law was mainly the quality of "Beers" at that time. At that time, spices used were fruits, herbs, weeds such as anis, myrtle, oak leaves, ivy (poisonous), along with the poisonous seeds of herbstzeitlosen, raspberries, elderberry, caraway, lavender, dandelion, bay leaves, balm, mint, nutmeg, cherry leaves, plums, rose leaves, rosemary, wild rosemary, schluessel flowers, juniper berries, and lemon were normally used for brewing. Thereby, there were certain reasons for these uses. As an example, some ingredients were used as a substitute for hops, others for the intoxicating effect, others to extend the shelf life. It is easy to see that beers at that time had little to do with what we know today as beer.
The Purity Law:
How beer is to be brewed and served throughout the duchy in Summer and Winter.
We decree, lay fast and demand with the advice of our agricultural community, that from here on, throughout the duchy of Bavaria to include the countryside as well as in our cities and villages, which do not as yet have a specific ordinance in place, that from St. Michaels feast day to feast day of St. George, a Mass (1.069 bavarian liters) or a Heat (a half ball shaped vessel not a full Mass) not more than one Penny Munich Currency and from St. George day to St. Michaels feast not more than two Pennies of the same currency, the Head for not more than three Heller (one Heller = ? penny), will be punished under below listed conditions.
Who however is not brewing a Maerzen beer, but rather some other beer, or wishes to have some other type, he may not sell the beer under any circumstances for more than one penny per Mass.
We especially demand that from now on and forever in our cities and villages as well as in the country, that no longer any materials for beer brewing will be used other than Barley, Hops and Water. Whoever shall knowingly break these laws or does not adhere to them, will be sentenced by the superior court to immediately remove the keg of beer. However, where a tavern keep is served by a beer brewer in our cities, villages or in the country, two or three pails (60 mass) on the community of farmers, shall be himself alone forbidden the Mass or a Kopf beer by one Heller more as described above. Also, we as Dukes have the responsibility that if the price of barley should rise due to shortage caused by weather, we will cause the sales of beer to be diminished or regulated to assure the law is maintained.