Who are the "Visitors" in the chapter "Solitude"

The visitors aren't named. Thoreau simply says they exist. It would seem that Thoreau lived close enough to town that they could walk to his cabin,

"I could always tell if visitors had called in my absence, either by the bended twigs or grass, or the print of their shoes, and generally of what sex or age or quality they were by some slight trace left, as a flower dropped, or a bunch of grass plucked and thrown away, even as far off as the railroad, half a mile distant, or by the lingering odor of a cigar or pipe. Nay, I was frequently notified of the passage of a traveller along the highway sixty rods off by the scent of his pipe. "

Suffice to say Theoreau includes visitors as part of his simple life. Hey they even come when he's not home!