The crystal, used as a tool by mediums and for curing disease, belonged to maverick philosopher, mathematician and astrologer John Dee, a consultant to Elizabeth I. He lived between 1527 and the turn of the 17th Century, becoming a leading authority on “angel-magic” and beliefs that man had the potential for divine power. Also taken was a statement about the crystal’s use by author and pharmacist Nicholas Culpeper, written on the reverse of ancient deed manuscripts in the mid-1600s.
Here's an entertaining report on Dee from the "occultopedia": John Dee, the Queen's astrologer.
Unrelated except to Dee-- Searching the Guardian for Dee articles, I hit on a cool piece about an attempt to decrypt the Voynich manuscript's code:
"The Voynich Manuscript, bought by Rudolph II of Bohemia in 1568, mystified cryptographers and linguistics experts alike. Until, that is, a senior lecturer in computer science at Keele University found a solution through a test run of a technique he intended for research into Alzheimer's. Dr Gordon Rugg's suggestion is that the manuscript, a handwritten book in a unique script that contains features found in no known language, was a hoax. It is probable, on his account, that the author was the 16th-century "con artist" Edward Kelley."
Kelley was a clairvoyant of Dee's, it seems. "There is evidence Dee had the manuscript in his possession for a long time - a leading authority on Dee has attributed the numbers on the pages to him."