Matthaeus Praetorius Memelensis Borussus (Matthaeus Praetorius, c. 1635 - 1704) was born in Memel (now Klaipėda in Lithuania) into a family of pastors. He studied in Königsberg (1650, 1655-1657) and Rostock (1657-1660) and obtained a master's degree. Besides Latin, he studied German, Lithuanian and Polish. From about 1663 to 1684 he worked in the Lithuanian parish of Niebudschen (today Krasnogorsk). In 1684 he converted to Catholicism and became the historian of the King of the Republic of Two Nations, the Polish-Lithuanian dual state. From 1688 to 1704 he worked in Pomerellen as a Catholic clergyman. He died in Neustadt (also Weyersfrey, today Wejherowo in Poland).
Praetorius wrote five historical and theological books in Latin. He also wrote (from about 1670 to 1698) the 18-volume manuscript Deliciae Prussicae or Prussian Showcase, one of the most comprehensive works on the history of the ancient Prussians and the Principality of Prussia, one of the earliest descriptions of Baltic mythology and ethnography. He drew on ancient sources and medieval chronicles, as well as historical works and travelogues from the 16th and 17th centuries. In addition, there were works on church history and, in particular, treatises on the history of the ancient Prussians and information about the way of life, customs, beliefs and language of the Prussians that he collected himself. He also relied on the works of Simon Grunau, Johannes Bretke and Christoph Hartknoch.