There's a permanent display in London Science Museum of King George III's collection of scientific instruments in 18th century. Consider Boyle-Hooke Vacuum pump made in 1659.
It is very hard and takes enormous effort to pump air out of the glass container. They sometimes used horses to pump air out. So, the question is: Why is it so hard to create a vacuum by pumping air out of the glass container? Where does the opposing force the prevents air from being removed come from?
Pictures of a Klein bottle, a pegasus computer and Babbage's Difference Engine here.
> Q: Where does the opposing force the prevents air from being removed come from?
A: The very large, and quite heavy column of air above our heads -- 15lbs/sq.inch or so. We live at the bottom of an ocean of air.
The force the horses push against is the weight of the atmosphere itself. In effect, they are lifting a column of air the height of our atmosphere.