Lime and sugar worked together with cachaça over ice. Brazil's national cocktail, three ingredients, and the whole technique is in how you treat the lime.
The lime is the whole drink. The juice gives acidity and the peel gives the aroma, which is why the slices are pressed against the glass and the peels go into the shaker. What you must not do is grind the white pith, which is bitter and cannot be taken back out. A caipirinha is more commonly made by muddling lime and sugar directly in the glass and pouring the cachaça over, which is simpler than this shaker method and gives much the same result. One ounce of cachaça is modest: most versions use closer to two.