Musannaf Ibn Abi Shayba 9:492

Waki’ narrated to us, from Abu Hilal, from Ibn Sirin, who said: ‘Amr ibn Hurayth proposed to ‘Adi ibn Hatim for his daughter, but he refused except on his own terms. So ‘Adi judged [the dowry to be] the Sunnah of the Prophet, [which was] four hundred and eighty [dirhams]. Then ‘Amr sent ten thousand [dirhams] to him, and he said: "Prepare her [with it]."