Now here's a conundrum. Looking for the source of the quote:

"Dancing is the vertical expression of horizontal desire"

The first web reference I found credited Robert Frost the American Poet.

But there is a contra dance band called "Vertical Expression" and a band member insisted it was George Bernard Shaw. It is the kind of thing he would say but .......

My problem is that I am sure they both said such and my first encounter (from radio and I think credited GBS) was the quote:

"Dancing is the perpendicular expression of horizontal desire made legal by music"

Now can anyone with a dictionary of quotations put a firmer stance on this? With the best will in the world and without Wiki on this one, I am struggling.
The web in general is not helpful enough, there are a lot of opinions backed up by conviction and little else.

TIA