Remy Le Mercier, a 16th-century tax collector from Halle, has been cited repeatedly by historians, past and present, for an ordinance he issued in 1559. The document prescribes the precise proportions of grains to be used in the local beer types “keut” and “houppe.” Brewers who deviated from these proportions were to be fined.

Today, the Halle ordinance is regarded as the oldest known reference to the origin of the lambic beer style — thanks to its specific grain ratios and geographical context.

Unusual by today’s lambic standards, however, is the mention of oats among the ingredients — a grain no longer found in modern lambic breweries. Yet, a composition of 10 % oats alongside at least 60 % barley malt and 30 % unmalted wheat would still meet current legal requirements for lambic.