I've had a great time in South America and South Africa. Indeed it now seems that on this pair of wild hot continents I've enjoyed the most fruitful year of my life.

letter to William Colby (4 February 1912); published in "John Muir — President of the Sierra Club", by William E. Colby, Sierra Club Bulletin, volume 10, number 1 (John Muir Memorial Issue, January 1916) pages 2-7 (at page 6); and in John Muir's Last Journey, edited by Michael P. Branch (Island Press, 2001), page 160