We've been reading a history of how alchemical secrets were passed down via various coded messages woven into different philosophies and religions through the ages.  In The Mysteries of the Great Cross of Hendaye: Alchemy and the End of Time (a companion to Fulcanelli's Les Mystère des Cathèdrales, about how the cathedrals of Europe aren't churches but rather stone books hiding the wisdom of alchemy in plain view), we learn on page 214 that the esoteric motive behind cathedral building was to make living grails that house the spirit of the (Mary precursor) black madonna/goddess Isis as a tangible "mystereion" designed to last through the centuries.  We took a photo at Exeter Cathedral two years ago, and back then we didn't have eyes to see the holy grail.  We've lately been ruminating on how a third party might be able to experience the grail-ness of a cathedral without having to read in advance a 200-page explanation, and it occurred to us that lens flares can distill the gnostic light that cathedral windows channel.  Then we remembered the Exeter Cathedral photo, and sure enough — there was the grail!  (We did an overlay of a chalice to clarify what we're seeing in our photo.)