Klimt and Da Vinci
I bought 2 old, used books for $2 each - one book of Klimt figure drawings and another one a set of B and W Artists' drawings and paintings of hands (Heidi Lenssen: Hangs in Nature and Art).
These are both excellent books for me to use to make copies of drawings by Master Artists. Here is a Klimt portrait and hands drawn by Leonardo DaVinci. Both were drawn with graphite.