Bhutanese painting has developed over the centuries from techniques in neighbouring countries into an original display of master craftsmanship by traditional painters (Lhadrips) whose work, including murals and frescoes, adorn the walls of massive dzongs, temples and monasteries. Traditional symbols and motifs, chosham (altar), thangka or thongdroel (religious scrolls) with the images of Buddha and other deities are a trademark of traditional art painted following precise, symbolic iconographic rules codified in ancient Buddhist texts. They depict the relationship that human-beings share with nature, animals and religion. Another singular feature of Bhutanese paintings is anonymity. Lhadrips never sign their work as an act of humility and devotion in the service of the larger religious symbolism of the painting. Natural earth pigments (sa-tshoen) are employed in traditional Bhutanese paintings, known by their common names sa–na, “black earth,” sa-tsag, “red earth” and sa-ser or “yellow earth”.