Let them sleep in complete silence, try to bring them inside your home if possible because any oncoming cars are going to destroy their sleep. But if you were to try to bring the cats inside your home, it would only result in total and utter annihilation of their deep slumber. It seems counterintuitive because they will consider you with extreme hostility if you disturb their sleep.
The expression on that cat is of pure contentment. We wonder if humans can experience the same level of peace. Imagine lying on your bed without a worry in the world, without having to fear missing out on paying your bills and getting your groceries in order. But as humans we have far too many concerning matters to tend to before finally collapsing on the bed with the sheer exhaustion.