From 'Horse, Saddles, and Bridles', by Colonel William Carter, 1902. The book goes into great detail on lessons learned in the Civil and Indian Wars regarding maintaining horses, endurance, equipment, and standard practices in the U.S. Cavalry.
The U.S. Cavalry saddle weighed ..... 17 lbs.
Total equipment weight (including saddle, guns, boots, etc) .... 90 lbs.
Maximum allowed weight of Cavalry trooper .... 165 lbs.
Prefered weight of Cavalry trooper .... 130 to 150 lbs.
Total weight on horse .... 220 to 255 lbs.
Average weight of US Cavalry horse (10 regiments) ... 1052 lbs.