For the base: Pour the rye whiskey into a 4-quart container. Fill the now-empty rye whiskey bottle with water, pour into an electric kettle, and bring to a boil. Add the sugar and stir until the temperature drops to 190ºF. Place the tea bags in the kettle and steep for 3 minutes.
Add the tea, rum, and Cognac to the whiskey. Add the lemon zest to the mixture, wrapping and reserving the lemon bodies for later use, and stir to combine. Cover and refrigerate overnight.
For the punch: Strain the base into a large punch bowl. Juice the reserved lemon bodies and add to the punch bowl. When ready to serve, add the oranges, lemons, sparkling wine, and seltzer water, and stir to combine. Add the ice block and serve with freshly grated nutmeg.