The Not Sourdough make your own yeast method?

I know way back when the only way to get yeast was from the air, and that once the dough was innoculated people were able to save back a little and use it for the next day. Supposedly by mixing in that bit, rising the dough, and then saving out a bit for tomorrow or whenever you never need to buy yeast.
Has anyone experimented with this method yet? I did, but it was summer (no AC) so I kept the cup of dough in the fridge because I don't eat a loaf a day, and it just didn't work out.