Crush berries, sweeten to taste, and let stand 1 hour. Add Minute Tapioca and salt to water, and cook in double boiler 15 minutes, or until tapioca is clear, stirring ferquently. Add butter, berry juice, and sugar. Remove ffrom fire; add berries and lemon juice. Chill until firm. Serve in sherbet glasses. Garnish with sweetened, whipped cream and a few whole berries. Serves 8. If canned berries are used, they should be drained and sugar omitted.