Lenin, while been in prison used to write in milk on shoulders of the books that his family was bringing in for him to read. When books were returned to family they would heat pages which made letters to appear.
the story also goes that, since he was only given milk and bread while in solitary confinement, he would make inkwells out of bread, in order to write with said milk. I can't remember off the top of my head what he used as a writing utensil.
I can't remember off the top of my head what he used as a writing utensil.