Rub a lime wedge around the rim of each margarita glass, then dip the rim in a shallow plate of coarse salt and set the glasses aside.

Pour the tequila, orange liqueur, lime juice, and agave syrup into a 2-quart pitcher.

Stir the mixture with a long spoon for about 20 seconds, until the agave syrup disappears into the liquid and no streaks remain at the bottom.

Cover the pitcher and refrigerate it for at least 1 hour and up to 2 days, so the flavors have time to settle together.

Fill each salt-rimmed glass with ice, then pour the margarita mixture over the top to about half an inch from the rim.

Hook a lime wheel onto the rim of each glass and serve right away, while the ice is still cracking.