His adopted son Petar II Petrović Njegoš ruled from 1830 until 1851. It is recorded as one of the greatest educators of the Serbian people in general. He wrote one of the most important works of the romantic epoch "Mountain Wreath" (regarded as one of the artistic foundations of Serbian nationalism), and he was also credited with bringing the final look of a Montenegrin hat, which is decorated with a black frame and represents the crown, more precisely, sorrow for the slavery of the Serbian people under Ottoman yoke. The top of the cap is red, symbolising blood, where 5 golden threads are engraved, thought to signify 5 centuries of slavery under the Turks. Within these golden threads there is a "Cross" with four Cyrillic letters (scores) S, a variant of the Byzantine Palaiologos tetragrammic cross, sometimes referred to as the variant of the Serbian cross.