Silverpoint drawing of Leda. Credited to Leonardo Da Vinci between 1505 to 1507. 
I remember looking at the originals on loan from the London Museum in Melbourne at the NVG. Drawn with a silverpoint pen on paper coated with crushed bone (Vellum)  to create a rough surface. It was dark as direct light would impact on the drawings.
 The drawings of Leonardo da Vinci, Leonardo da Vinci, "Study for the Head of Leda, c. 1505-7"
 Vellum, Wikipedia, "An animal skin, usually calf, prepared by cleaning, stretching and
scraping. Tension is created by drying and wetting. The final surface
is covered with a ground bonemeal (finely ground up animal bones)
mixture which gives the surface a rough texture suitable for
en.wikipedia.org/wiki/Vellum. I remember toying with the idea of creating some vellum and trying Silverpoint. The masters used techniques that allowed their works to survive hundreds of years.