Toynbee Tiles History Discussion
The two copies of Arnold Toynbee's Experiences in the collection of the Free Library of Philadelphia. One of these is likely the copy that originally inspired the mysterious tiler. Also shown is the Library's copy of Resurrect Dead: The Mystery of the Toynbee Tiles, Jon Foy's 2011 documentary exploring the story behind the tiles.
For coverage of the event, see On Technology and Media, "Toynbee Tiles: Recent Developments and Mysteries Anew."