I was lucky enough to see Rauschenberg’s Dante’s Inferno at the Whitechapel Gallery in London in 1964 – my second year at art school – and it was a revelation. I’d seen repros of his work in art magazines (Studio International was the favorite ‘zine then), but looking at this extraordinary suite of thematically linked drawings-cum-rubbed-off montages – at the subtlety and delicacy of the densely figured images, was a spiritual experience. Rauschenberg – always a formal innovator as well as a brilliant imagist and painter – had evolved a technique of using  spirit-based solvent (there was a product called Polyclens that worked)  applied to the reverse side of a commercially printed image (from a magazine or newspaper) and then he simply rubbed the reverse side with a burin to create a mirror-image rub-off of the printed image on his drawing paper. This gives you some indication:

Rauschenberg: Canto XIV: Circle Seven, Round 3. The Violent against God, Nature and Art, from the series Thirty-Four illustrations for Dante’s Inferno 1959-60.

(image courtesy Rauschenberg Foundation)

see Mary Kotz: Rauschenberg: Art and Life 2004