In a food processor grind fine the whole almonds with the sugar and salt. In a bowl beat the whites until they are foamy (just before they hold soft peaks) and fold in the almond mixture gently but thoroughly. Line a large baking sheet with parchment paper and butter the parchment. Spoon the batter onto the parchment, 2 inches apart. Bake the macaroons in the middle of a preheated 300 degrees F. oven for 15 to 20 minutes, or until they are golden around the edges, and let them cool on the parchment. Peel the macaroons from the parchment and store them in an airtight container.