What societal critic contributed to the anthology "Excursions"? 
Excursions (anthology):  The anthology contains an introduction entitled "Biographical Sketch" in which fellow transcendentalist Ralph Waldo Emerson provides a description of Thoreau. Ralph Waldo Emerson:  He was seen as a champion of individualism and a prescient critic of the countervailing pressures of society, and he disseminated his thoughts through dozens of published essays and more than 1,500 public lectures across the United States.
Ralph Waldo Emerson