Cf. also this base metal specimen.
Polybius 10.27 says…
Media is the most notable principality in Asia, both in the extent of its territory and the number and excellence of the men and also of the horses it produces. 2 It supplies nearly the whole of Asia with these animals, the royal stud farms being entrusted to the Medes owing to the excellence of the pastures. 3 On its borders a ring of Greek cities was founded by Alexander to protect it from the neighbouring barbarians. Ecbatana is an exception. 4 This city is situated in the northern part of Media and commands that portion of Asia which borders on the Maeotis and Euxine.5 It had always been the royal residence of the Medes and is said to have greatly exceeded all the other cities in wealth and the magnificence of its buildings.6 It lies on the skirts of Mount Orontes and has no wall, but possesses an artificial citadel the fortifications of which are of wonderful strength. 7 Beneath this stands the palace, regarding which I am in doubt whether I should go into details or keep silence. 8 For to those who are disposed to recount marvellous tales and are in the habit of giving exaggerated and rhetorical reports of certain matters this city affords an admirable theme, but to such as approach with caution all statement which are contrary to ordinary conceptions it is a source of doubt and difficulty.9 The palace, however, is about seven stades in circumference, and by the magnificence of the separate structures in it conveys a high idea of the wealth of its original founders. 10 For the woodwork was all of cedar and cypress, but no part of it was left exposed, and the rafters, the compartments of the ceiling, and the columns in the porticoes and colonnades were plated with either silver or gold, and all the tiles were silver. 11 Most of the precious metals were stripped off in the invasion of Alexander and his Macedonians, and the rest during the reigns of Antigonus and Seleucus the son of Nicanor, 12 but still, when Antiochus reached the place, the temple of Aene alone had the columns round it still gilded and a number of silver tiles were piled up in it, while a few gold bricks and a considerable quantity of silver ones remained. 13 From all the objects I have mentioned sufficient was collected to coin money with the king’s effigy amounting to very nearly four thousand talents.
In this passage of Lucilius (mid to late 2nd cent BC), Ecbatana is being used symbolically as the furthest limits of the known world. The joke may turn in part on those with such bad geography that they thought one could sail a ship there.