The story of Henry David Thoreau's essay: "A Walk to Wachusett."  The first of Thoreau's Excursions essays is described in great detail as the author walks along the route traveled by Thoreau and companion Richard Fuller in the summer of 1842 from Concord to the summit of Mt. Wachusett in Princeton.   The book is rich in providing sources of the material used in his essay.  An appendix provides detailed directions on how to make the journey today.