"Walden"
I think reading "Walden," is the most influential of all the books I've read, especially the chapter, Where I Lived and What I Lived For.

Once while in NYC, with my wife and young daughter, I made a "pilgrimage" to Walden Pond and followed a trail through the woods to Walden Pond and to Thoreau's cabin. This was long before it was recognized as an important historical site, and there were no signs or anything that recognized the location. It's a big deal now. Being young and naive, I picked up a small rock from the foundation to the fireplace. It's now one of my prized possessions, although I shouldn't have picked it up. But, I didn't know any better at the time.

It looks like an ordinary rock, but it's not.

It's meant as a reminder of how important I think understanding Thoreau is. My actions are my values.