Techniques include drawing with fingers or charcoal, applying pigment with ‘brushes’ made of hair or moss, and blowing the pigment on a stencil …with, for instance, a hollow bone.
4 Essentials for Drawing

Techniques include drawing with fingers or charcoal, applying pigment with ‘brushes’ made of hair or moss, and blowing the pigment on a stencil …with, for instance, a hollow bone.
It was critical observation that allowed Sir Isaac Newton to define gravity after watching an apple fall to the earth from a tree.