Since when does X mark the spot?

General Questions
#1

There’s got to be an origin for the idea that X always marks the location on the map where the buried treasure is.

The question is, is it a real origin, in that there really was a map of buried treasure marked with an X?

It certainly is realistic: a monochromatic map done with ink and parchment wouldn’t use color to denote objects, but symbols. A big fat X is as good a symbol as any, provided you can tell it apart from a simple intersection of two lines; and it requires no literacy.

Or is this a fanciful origin, coming from a particular book or film?

#2

I though that was from Treasure Island? I really can’t remember it well enough, maybe a more literary Doper will confirm…

#3

While I haven’t done an exhaustive search, I can find it only as early as the 1900-1910 period.

#4

Well, it’s not in the early treasure-hunt stories the Gold Bug or The Musgrave Ritual. For some reasion, I’m thinking of Treasure Island, too, but I can’t recall if it’s actually in there.

#5

From Treasure Island:

““I’ll tell you what I’ve heard myself,” continued Captain Smollett: “that you have a map of an island, that there’s crosses on the map to show where treasure is, and that the island lies—” And then he named the latitude and longitude exactly.”

It seems like X’s to me.