The Light Bulb, the Motion Picture Camera...

Clue #4

"If our personality survives, then it is strictly logical or scientific to assume that it retains memory, intellect, other faculties and knowledge that we acquire on this Earth. Therefore, if personality exists after what we call death, it is reasonable to conclude that those who leave the Earth would like to communicate with those they have left here. I am inclined to believe that our personality hereafter will be able to affect matter. If this reasoning be correct, then, if we can evolve an instrument so delicate as to be affected by our personality as it survives in the next life, such an instrument, when made available, ought to record something."

- Thomas Edison, Scientific American, October 1920