Vilem Rožmberk
William of Rosenberg (czech: Vilém z Rožmberka, german: Wilhelm von Rosenberg; 10 March 1535 - 31 August 1592) was a wealthy Bohemian count during the 16th century, born to a powerful family with interests in alchemy.
In 1545, following the death of his uncle and regent Peter V of Rožemberk he inherited his family's land in southern Bohemia. From 1560 to 1570 he served as the High Treasurer of Bohemia, under the Holy Roman Emperor Ferdinand I and Maximilian II and then as the High Burgrave of Bohemia until his death during the reign of Rudolf II.
William actively promoted science, literature, music and architecture. They created a library with a vast collection of precious manuscripts and incunables. With its approximately 11000 volumes, it was one of the largest libraries of its time. In 1586, the alchemists Edward Kelley and John Dee secured the patronage of Rožmberk, and moved from Prague to Třeboň. There, they communicated with the First Civilization using a Crystal Ball.
He was one of the last members of the House von Rosenberg, his brother Peter Vok being the last male member. Upon Peter's death in 1611 the House went extinct in the male line. Altough William married four times, he was childless.