He does not know when or how, but like Herodotus he blames the poets.[23] Amber is supposed to have come from there. Phaëthon, son of the sun, struck by lightning changed into poplars and exuded tears every year, which is the source of amber (a myth of Pausanias). Expressing surprise at the ignorance of the poets, Pliny says "There can be no doubt that amber is the product of the islands of the northern ocean (Baltic Sea)" and attributes its introduction into the Po valley to the Veneti, the last link in a trade route to the north through Pannonia and Germany.