When our poor, faultily sensitive vision can perceive a thing, we say that it is visible. When the nerves of touch can feel it, we say that it is tangible. Yet I tell you there are beings intangible to our physical sense, yet whose presence is felt by the spirit, and invisible to our eyes merely because those organs are not attuned to the light as reflected from their bodies. But light passed through the screen, which we are about to use has a wavelength novel to the scientific world, and by it you shall see with the eyes of the flesh that which has been invisible since life began. Have no fear! ("Unseen - Unfeared")
Francis Stevens, American Fantastic Tales: Terror and the Uncanny from Poe to the Pulps
intangible, invisible, perception, senses