The pignora imperii ("pledges of rule") were objects that were supposed to guarantee the continued imperium of Ancient Rome. One late source lists seven. The sacred tokens most commonly regarded as such were the Palladium, the wooden image of Minerva (Greek Athena) that the Romans claimed had been rescued from the fall of Troy and was in the keeping of the Vestals; the sacred fire of Vesta tended by the Vestals, which was never allowed to go out; and the ancilia, the twelve shields of Mars wielded by his priests, the Salii, in their processions, dating to the time of Numa Pompilius, the second king of Rome.