On his first day as a mail carrier, Sam Wilson noted that inscription, cribbed from Herodotus, on the General Post Office, and took it to heart: "Not snow, nor rain, nor heat, nor gloom of night stays these couriers from the swift completion of their appointed rounds." It couldn't be literally true, of course. Given a real blizzard, it would be impossible to make his way through the pathless drifts; and if there had been a major flood, he could hardly have swum to deliver letters to the marooned