Dr John Dee's Obsidian mirror

"This mirror was used by the Elizabethan mathematician, astrologer and magician John Dee (1527-1608/9) as a 'shew-stone', one of many polished translucent or reflective objects which he used as tools for his occult research."

The Black Stone into which Dr Dee used to call his spirits

"John Dee who was the unofficial court astrologer of Elizabeth the First. He was the man who invented the concept of the British Empire—he was the first one to use the phrase. He was very much at the heart of the Elizabethean Secret Service."
" Without John Dee, there wouldn’t have been an Isaac Newton. The science of navigation was practically invented by John Dee. He was a classic Renaissance man"