Carefully pick any thorns from the caper leaves and put them, together with buds, in jar. Make brine mixture: Measure enough water to cover the capers into a glass measuring cup. Add salt one tablespoonful at a time, until an egg placed in the water floats with about a quarter-sized piece of its shell above the water. Stir brine and pour over capers. Place lid on tightly and leave in a cool, well-ventilated place. Change water daily for about two weeks, until capers have absorbed briny flavor. Add vinegar, stir, and store jar in refrigerator; to serve salad, simply remove capers and leaves with a slotted spoon, place on plate, and garnish with lemon slices.