"David Brewster, a nineteenth-century scientist… observed a related form of stereo illusion. Gazing at wallpaper with small repetitive motifs, he observed that sometimes, with the proper convergence or divergence of gaze, the patterns might quiver or shift and then jump into startling stereoscopic relief, seeming to float in front of or behind the wallpaper.
…it seems likely that such “autostereograms” have been experienced for millennia, with the repetitive patterns of Islamic art, Celtic art, and the art of many other cultures. Medieval manuscripts such as the Book of Kells or the Lindisfarne Gospels, for example, contain exquisitely intricate designs done so exactly that whole pages can be seen, with the unaided eye, in stereoscopic relief. (John Cisne, a paleobiologist at Cornell, has suggested that such stereograms may have been “something of a trade secret among the educated elite of the seventh- and eighth-century British Isles.”)
In the past decade or two, elaborate autostereograms have been widely popularized in Magic Eye books." - Oliver Sacks, The Mind’s Eye
Those unfamiliar with "Magic Eye" books can read about them at Wikipedia. The embedded image is "Geometric arabesque tiling on the underside of the dome of the Tomb of Hafez in Shiraz." For extensive research on Islamic design, visit the Catnaps.org website..
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