Rudolf II (July 18, 1552 – January 20, 1612) was Holy Roman Emperor (1576–1612), King of Hungary and Croatia (as Rudolf I, 1572–1608), King of Bohemia (1575–1608/1611) and Archduke of Austria (1576–1608). He was a member of the House of Habsburg.
Rudolf's legacy has traditionally been viewed in three ways: an ineffectual ruler whose mistakes led directly to the Thirty Years' War (Wikipedia page ); a great and influential patron of Northern Mannerist art - he was a noted patron of the arts; and a devotee of occult arts and learning which helped seed the scientific revolution.
Astrology and alchemy were mainstream science in Renaissance Prague, and Rudolf was a firm devotee of both. His lifelong quest was to find the Philosopher's Stone and Rudolf spared no expense in bringing Europe's best alchemists to court, such as Edward Kelley and John Dee. Rudolf even performed his own experiments in a private alchemy laboratory. When Rudolf was a prince, Nostradamus (Wikipedia page ) prepared a horoscope which was dedicated to him as 'Prince and King'.
From a 1666 letter that accompanied the manuscript when it was being sent from Johannes Marcus Marci to Athanasius Kircher, it appears that the Voynich Manuscript once belonged to Emperor Rudolf II (1552–1612), who paid 600 gold ducats for it.
The BBC Radio 4 'In Our Time' on Rudolf II program was transmitted on Thu 31 Jan 2008 - more details at  and the Wikipedia page on him is . A list of people associated with his court is here . An article on Prague in his time is here . There are numerous other webpages on him.