At least a day ahead, fill a 2-quart bowl with water and freeze until completely solid.
In a large punch bowl, muddle the lemon peels and sugar.
Let the mixture stand for at least 3 hours.
Add the boiling water, stirring until as much as possible of the sugar has dissolved.
Add the remaining ingredients and stir to combine.
To serve, add the ice block and garnish liberally with freshly grated nutmeg.
This recipe serves 25.