Caxton's Unicorn paper watermark
"In the middle of the workshop stood the press, a great wooden erection secured between two upright posts that ran from floor to ceiling. Bendy gazed at it, full of awe. He had seen a press before; the binder who bound books for the Crowing Cock had one of the same shape -- with a heavy board that moved up and down by a big vertical screw. But the binder's press was tiny. This was a monster."
" 'Of course the press is no new thing,' said Caxton. 'It is the type which is new. The old way of pressing paper on to a carved block is useless for books; you need a new block for every page. Now we have all the letters of the alphabet cast in metal, each letter separate, and we build up a page word by word and letter by letter. When we have printed enough copies we pull the type to pieces again ready to set up for another page. Come and see for yourselves.' "
The Load of Unicorn Cynthia Harnett (text and illustrations)