In the 1970s when I was in grade school we attached postcards to helium balloons to see how far they could get (some people got responses that indicated they tr

In the 1970s when I was in grade school we attached postcards to helium balloons to see how far they could get (some people got responses that indicated they traveled for hundreds of miles). That probably would be even less acceptable today in terms of littering as deflated balloons often get eaten by wildlife to ill effect.