Preheat the oven to 375 F. Place 1 lemon inside the cavity of the cleaned duck. Cut 4 slices from the other lemon. Squeeze the juice from the 2 ends into a cup and reserve. Put the duck into a flame proof casserole. Add the water, onion, ginger, and salt. Bring the liquid to a boil. Cover the casserole, transfer it to the oven and cook for 1 1/4 hours. Remove the casserole from the oven, Lift out the duck. Strain the cooking juices and skim off the fat. Return the strained juices and duck to the casserole. Pour the wine over the duck. Return the casserole to the oven and roast for 30 minutes, or until the duck is cooked. Sprinkle the duck with the reserved lemon juices, garnish with lemon slices, and serve from the casserole.{$7e}(Original recipe for 4)