Pony Express mochila
A Pony Express mochila (Spanish, pronounced [mo-chee-lah], for "knapsack", "pack", "pouch") was a removable lightweight leather cover put over a horse saddle for carrying mail and was used by the Pony Express. Riders of the Pony Express made quick exchanges to new fresh horses, usually within a few minutes, at each remount station on their route across the United States.