Have you ever buried a time capsule?

I think we made one in kindergarten, but I bet it's long gone. I know there's one buried outside this museum in town when we were celebrating it's 100th anniversary of townshipness back in like 1997. I was sitting on the bricks on this sign right above where they buried it. I have no clue what's in it.

What would you leave behind in a capsule for the people of the future?