Rinse the rice. Cover with water and soak for 12 hours. Drain.
Wash the almonds, cover with water, and soak for 6 to 8 hours. Shell the almonds and slip the skins off them. Discard the shells and skins.
Puree the rice in a blender. Set aside.
Puree the almonds, to a fine paste, in a blender.
Mix the rice, almond paste, cinnamon, sugar, and the 6 quarts water, in a large glass jar or clear pitcher. Refrigerate until chilled.
Serve the horchata in tall glasses over ice cubes.
c.1997, M.S. Milliken & S. Feniger, all rights reserved