Charles-Francois Tiphaigne wrote "Giphantia" in 1761 which contains a passage which seems to presage photography, or rather emulsion..
"The elementary spirits, are not so able painters as naturalists; thou shalt judge by their way of working. Thou knowest that the rays of light, reflected from different bodies, make a picture and paint the bodies upon all polished surfaces, on the retina of the eye, for instance, on water, on glass. The elementary spirits have studied to fix the transient images: they have composed a most subtle matter, very viscous, and proper to harden and dry, by the help of which a picture is made in the twinkling of an eye. they do cover with this matter a piece of canvas, and hold it before the objects, and hold it before the objects they have a mind to paint. The first effect of the canvas is that of a mirrour; there are seen upon it all the bodies far and near whose image the light can transmit. but what the glass cannot do, the canvas, by means of the viscous matter, retains the images. The mirrour shows the images exactly; but keeps none; oure canvases show them with the same exactness and retain them all. The impression of the image is made the first instant they are receive on the canvas, which is immediately carried away into some dark place; and hour after the subtle matter dries, and you have a picture so much the more valuable, as it cannot be imitated by art or damaged by time."