The Iliad by Homer Book 24 Page 41

Even lovely Niobe had to think about eating, though her twelve children — six daughters and six lusty sons — had been all slain in her house. Apollo killed the sons with arrows from his silver bow, to punish Niobe, and Diana slew the daughters, because Niobe had vaunted herself against Leto; she said Leto had borne two children only, whereas she had herself borne many — whereon the two killed the many.

Nine days did they lie weltering, and there was none to bury them, for the son of Saturn turned the people into stone; but on the tenth day the gods in heaven themselves buried them, and Niobe then took food, being worn out with weeping. They say that somewhere among the rocks on the mountain pastures of Sipylus, where the nymphs live that haunt the river Achelous, there, they say, she lives in stone and