I happened upon this benedicto by Edward Abbey while perusing my copy of Campfire Stories: Tales from America’s National Parks.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view. May your mountains rise into and above the clouds. May your rivers flow without end, meandering through pastoral valleys tinkling with bells, past temples and castles and poets’ towers into a dark primeval forest where tigers belch and monkeys howl, through miasmal and mysterious swamps and down into a desert of red rock, blue mesas, domes and pinnacles and grottoes of endless stone, and down again into a deep vast ancient unknown chasm where bars of sunlight blaze on profiled cliffs, where deer walk across the white sand beaches, where storms come and go as lightning clangs upon the high crags, where something strange and more beautiful and more full of wonder than your deepest dreams waits for you—beyond that next turning of the canyon walls.
So long.
The original source appears to be the preface (dated June 1987) for the 1988 reprint of Desert Solitaire (p.12).