Humorous story I wish I had a photo of...
My wife and I were in a little restaurant in Waterton NP, Alberta (just across the border from Glacier Park) and she used the Ladies Room before getting our lunch. The restaurant was decorated with lots of old train station and railroad memorabilia. After a few minutes, she returned and told me while she was sitting on the throne, there was a sign in the stall that read "Do Not Flush While Train Is In the Station."
She said she wasn't sure what to do... after all, how could she tell if there was a train at the station several blocks away? She finally realized it was a sign taken from a passenger train lavatory, but had to reason it out before leaving.