That is radically different from a innerspring mattress. But even outside of futon mattresses, prior to the 19th century, mattresses were essentially just thic

That is radically different from a innerspring mattress. But even outside of futon mattresses, prior to the 19th century, mattresses were essentially just thicker futon mattresses. Heavy, prone to sagging, breeding ground for all sorts of vermin depending on the filling material, mattresses weren't super great.