Kublai Khan received an ornate letter signed by Marco Polo: "In Madrid, City of Lost
    Things, no item remains where it was set. If one drops his key in the dirt, he may
    never re-enter his home, and, even if he manages to stoop and recover the key, he may
    rise to find a tulip garden where his house once stood. In complementary fashion,
    things lost by others are forever turning up: A pocket watch on a coffee table. A fond
    memory in your recollection. I even know of a prince who turned up in a prison cell.
    When he appealed to the guards for his release, he failed to find the crown on his
    head, and when he was asked his name, he searched his thoughts, but could not find it.
    Indeed, the only hope now for the release of this prince of Spain is for you to send
    back 300 ducats for his release. Of course, he will reward you handsomely once he is
    out. Yours truly, Marco." Kublai Khan cocked an eyebrow and declared before his court,
    "Hey, everyone: Looks like we're about to get ripped off by the guy who traded gold
    for paper!" The court erupted in booming laughter.
                              — Italo Calvino, Invisible Cities 2: This Time It's Visible.