Well. if to only offer me own experience... A group of me mates were touring St. Augustine Fort some 25 years ago. We entered the Chapel area, and decided to hop the stantions and travel the long (150 metre) hallway to the old cloisters. About midway through, we were passed by a monk, clad in brown broadcloth or wool, an as we turned to watch him pass, he vanished. Dissapated, as it were, into the thin air. There was not other available exit, and we all had our eyes on him to see if he'd alert the docents. He just "melted" into the sunbeams. We turn about and ran from the place, all 6 of us exclaiming how utterly cold we were. The date was June 16th, 1981. I've no evidence beyond me own words. But that's the truth of it, and I'll stake me own life on it's veracity.