If you look at the moon on the horizon upside down through your legs the illusion that it is large goes away.

And if you drop your trousers while you are doing that, the people behind you can see the man in the moon

Now you're just trying to make me look silly!

You may look silly but it works.

Back when I was an MIT undergrad in the early 1970's I got a ride back to eastern New York for Thanksgiving or Christmas break with several other MIT students. That evening, the moon appeared very large, and I mentioned it was just an illusion. (I had read the July, 1962 issue of Scientific American growing up and knew about the illusion--it was the cover story.) Try as I might, I could not convince the others in the car that it was an illusion.