I love the immediacy and reality of this vignette, recounted by da Vinci regarding an event in his youth. Page 13.
Driven by my eager desire and wishing to see the multitude of varied and strange forms created by nature, and having wandered some distance amongst overhanging rocks, I came to the entrance of a great cavern, in front of which I stood for some time, astonished never having seen such a thing before. Bending forward, I rested my tired hand on my knee and held my right hand above my furrowed eyebrows as I peered down. I shifted from side to side, to see whether I could discern anything inside, but this was prevented by the deep darkness within. After having remained there for some time, I felt the contrary emotions of fear and desire arising within me — fear of the forbidding dark cavern, and my desire to see whether there was anything marvelous within it.I have stood in just such a fashion before caves and crevices in Sweden, America, Greece, Australia and elsewhere and know exactly the feeling he describes. Go or hold? Fear and desire. Of course, you always go - the human instinct for exploration is that strong.