The hymn to Ninkasi
Among the oldest texts that describe brewing is a Sumerian poem addressed to Ninkasi, the goddess of beer. It survives on clay tablets from about 1800 BCE and is usually called the Hymn to Ninkasi. It reads as a prayer, but each stanza names a step in the process, which may be why it was memorised: the poem works as a recipe that can be sung.
The steps are recognisable. Barley is made into malt, and bread, which the Sumerians called bappir, is baked from it. The bread is crumbled into water, mixed with more malt and sweet additions, and left to ferment. The liquid is then filtered through a mat into a collecting vat.
Not quite a modern beer
The result was thick and probably sweet and low in alcohol. It was drunk through reed straws from a shared vessel, which is how the tablets and seals of the period show people drinking it. Beer was also a ration. Texts from the cities of southern Mesopotamia list daily allowances of beer and bread for workers.
In the late 1980s a brewery in San Francisco made a trial version of the recipe with the help of an Assyriologist. The brewers admitted that parts of the poem could be read in more than one way, so the beer was an interpretation rather than a reconstruction.