Makyoh (Japanese for "Magic Mirror") are made of highly mirror-polished metal (usually brass) on the front face and engraved on the back face. From what I understand, it is currently commercially available as
toys! Also, check out
Makyoh in Action. Making these "Magic mirrors" often involved much intuition and skill in the past.
Now the basic idea behind the working of Makyoh is as follows: -
The front mirror side is illuminated by a parallel light beam, and the reflected beam is intersected by a screen. If the surface possesses "irregularities", the homogeneity of the reflected beam is perturbed and an image that can be related the surface morphology (I would assume some mapping function of sorts) appears on the screen. This "mapped" function is then called magical! In principle, there should be some sensitivity bound for the the roughness of the mirror-side.
The talk focused on attempting to digitize the craftsmanship of the early Makyoh workers using NC machining. All the steps involved in making Makyoh namely forming, casting, taking the pattern away and polishing were performed. Optimal machining conditions were identified first using a single drill hole and later on, using a series of drilled holes.
The reason why I find this interesting is that this problem in a way represented the reverse problem of
Makyoh topography which has been used to characterize the flatness of semiconductor wafers for some years now. A scientific work undertaken solely for the purpose of restoring temple architecture seems quite extraordinary.