floating down the river

[docs (imported)]

There used to be a radio show (remember radio before it became full of screamers and blowhards) called Can You Top This.....It starred some burlesque comedians who told jokes in and effort to top the other guy's joke (there was an audience laugh meter) Anyway....the show always was introduced the same way: Two men were floating down the Mississippi River on a marble slab.....at that time the stage music came up and we never got the rest of the story? Anyone know it? I'll accept any version.