Musannaf Ibn Abi Shayba 33:1237

Abu al-Ahwas narrated to us, from Mansur, from Mujahid, regarding His saying: "And there will be circulated among them vessels of silver and cups having been made of crystal, crystal made of silver; they have determined them by [precise] measurement." He said: The vessels are the drinking cups, and the cups are the goblets. And "by measurement" means they are not full to the point of overflowing, nor are they lacking in measure.