To this kin also belong the most prized inclusions, the collectors' stones with liquid inclusions and gas libellae in them, with for more than a thousand years have roused the curiosity of thinkers of their time and provided the basis for Claudian's epigram about "rock crystal in which there was water". Possibly this description referred to the water-clear rock crystals from the Saint Gotthard district which are famous for their liquid inclusions.