"The mountains are calling and I must go......"

I love this quote from John Muir (1873) which comes from a letter he wrote to his sister. The full quote reads "The mountains are calling and I must go and I will work on while I can, studying incessantly. He was born on  21st April 1838 in Dunbar, Scotland and was a naturalist and conservationist. However the photo is of Harry about to set off on expedition