Optical Calcite “Iceland Spar”
3″ x 3″ x 1″ or similar
This is really beautiful stone that bends light waves. When placed upon text it will double the words. In crystal healing it is used to improve perception, clear chakras, and increase learning and memory abilities, which makes it perfect to accompany the pdf.
You can find optical calcite at pretty much every rock store, as it is fairly common. It is also available on ebay and through gem and mineral websites.
Here is a little link for you to learn more about it.
QED: The Strange Theory of Light and Matter by Richard P. Feynman
Front page would be printed in color on white paper, the rest of the PDF would be printed black and white on white paper.
The PDF would be printed and the optical calcite would be placed on top.