Wash the lemons with hot water. Finely rub the peel with a grater and squeeze the lemons.
Put lemon juice and 1 - 2 tablespoons of lemon zest with sugar, salt and tap water in a saucepan, heat and simmer for about 5 minutes or until the sugar has completely dissolved.
Remove the lemon syrup made in this way from the stove and let it cool down a little. Pour through a sieve into a sealable bottle, let it cool completely and store in the refrigerator.
Fill up the syrup with cold mineral water as required, in a ratio of about 1:10, and serve in glasses with a sliced lemon and ice cubes.
The amount of syrup produced is sufficient for approx. 2 liters of mineral water.