Hannibal and the vinegar

How Hannibal Barca and his army crossed the Alps to go in Italy to fight against Rome:

At last, when men and beasts alike were worn out by their fruitless exertions, a camp was formed on the summit, after the place had been cleared with immense difficulty owing to the quantity of snow that had to be removed. The next thing was to level the rock through which alone a road was practicable. The soldiers were told off to cut through it. They built up against it an enormous pile of tall trees which they had felled and lopped, and when the wind was strong enough to blow up the fire they set light to the pile. When the rock was red hot they poured vinegar upon it to disintegrate it. After thus treating it by fire they opened a way through it with their tools, and eased the steep slope by winding tracks of moderate gradient, so that not only the baggage animals but even the elephants could be led down.
-- Titus Livius, XXI, 37

Yes, vinegar. I'm full of admiration for this legendary hack.