In a 4-quart bowl or heat-proof pitcher, use the back of a wooden spoon to bruise 1/4 cup fresh basil leaves. Add lemon juice. Mix juice with sugar. Pour boiling water over juice mixture, stir to dissolve sugar. Add lemon rinds and pureed watermelon. Cover and refrigerate 2 to 3 hours. Remove and discard rinds. Strain through a mesh sieve into a pitcher. Add watermelon wedges and fresh basil leaves. Stir before serving. Makes about six (10-ounce) glasses over ice.