In the late-70s I was working in central London and living in a ground floor flat in Stamford Hill adjacent to the Lubavitch. There was almost no heating and ice formed in the toilet. One way to warm up was to drive into the British Museum on a Sunday afternoon, and spend a few hours in relative warmth.
You could do that in those days … jump in the car, drive into London, and park at the back of the Museum. I doubt that it took more than 20 minutes each way. I would almost always go to the black obsidian mirror attributed to Dr. John Dee and spend some time scrying in it. You could do that too in those days … co-opt occult display items into private sessions without the formality of booking. I think Dion Fortune did something similar in the Assyrian section (see The Winged Bull).
There is a handwritten note from Horace Walpole: “The Black Stone into which Dr Dee used to call his spirits…”. Over the course of a few years I developed a detailed fantasy about this mirror. It was an Aztec scrying mirror dedicated to the dark god Tezcatlipoca. It was given to Dee as a gift by his friend Sir Walter Raleigh, and was probably looted from the Spanish.
As it happens, it really is an Aztec mirror. Chemical analysis has identified the mine where the obsidian was found, and you can read about it in this Smithsonian article.
However … (sadface) … the link to Dee is very circumstantial – see p.30 of John Dee’s Conversations with Angels by Deborah Harkness. According to Harkness, the mirror is never mentioned in the Conversations, while other crystals are. Other than Walpole’s catalogue, there is no evidence the mirror belonged to Dee.
Nevertheless, obsidian mirrors are A Thing. They are an off-the-shelf item in Glastonbury. I have one myself.
