Quotes from Henry David Thoreau, "Walking"

When a traveler asked Wordsworth's servant to show him her master's study, she answered, "Here is his library, but his study is out of doors."

But the walking of which I speak has nothing in it akin to taking exercise, as it is called, as the sick take medicine at stated hours... but is itself the enterprise and adventure of the day. If you would get exercise, go in search of the springs of life. Think of a man's swinging dumbbells for his health, when those springs are bubbling up in far-off pastures unsought by him!

I think that I cannot preserve my health and spirits, unless I spend four hours a day at least — and it is commonly more than that — sauntering through the woods and over the hills and fields, absolutely free from all worldly engagements.