“Dancing is a perpendicular/vertical expression of a horizontal desire/idea/intent/urge” has been credited to playwright George Bernard Shaw (1856-1950), playwright Oscar Wilde (1854-1900) and poet Robert Frost (1874-1963). There is no documentary evidence that Wilde or Frost ever said this.
 
Shaw was credited in the New Statesman, on March 23, 1962, for having said “(Dancing is) a perpendicular expression of a horizontal desire.” This, however, was well after his death in 1950. Shaw’s writings are well known and the saying does not appear to be printed in them, but it’s possible that Shaw made the statement in an interview that has not been recorded in print.
 
   
Google Books
Revolt Into Style:
The Pop Arts in Britain
By George Melly
London: Allen Lane
1970
Pg. 63:
I report what went on in three very different places where my fellow-countrymen and women had come together to give what Shaw called ‘a perpendicular expression of a horizontal desire’.
 
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If We Dream Too Long
By Poh Seng Goh
Singapore: Island Press; sole distributor: Angus & Robertson
1972
Pg. 85:
The only reason for dancing, as far as he could see, was the thrill of touching, of feeling some female body. What was called, appropriately, cheap thrill. Or, as someone in school said of dancing, the vertical expression of a horizontal desire.
 
Google News Archive
10 November 1972, Portsmouth (OH) Times, Ann Landers syndicated advice column, pg. 5, col. 2:
Dear Houston: Since you obviously consider dancing a vertical expression of a horizontal idea, it’s no wonder you and your wife are fighting about it.
 
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Florida’s Affair:
A Comedy in One Act
By Alan J. Levitt
New York, NY: Samuel French
1975
Pg. 16:
FLORIDA. Well, we were just dancin’. But to Henry’s way ‘a thinkin’ my dancin’ with that man was just a vertical expression of horizontal intention.
 
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Dirty Stories for All Occasions
By Andrew L. Cleveland
New York, NY: Galahad Books
1980
Pg. 43:
DANCING:
A vertical expression of a horizontal intention.
 
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The Greening of the Philippines
By Gary Lising
Makati, Metro Manila: G. Lising
1981
Pg. 102:
Dancing is a vertical expression of a horizontal desire!
 
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The Erotic Tongue:
A Sexual Lexicon
By Lawrence Paros
Seattle, WA: Madrona Publishers
1984
Pg. 26:
Oscar Wilde called dance “a vertical expression of a horizontal urge.”
 
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The Oxford Dictionary of Quotations
By Elizabeth M. Knowles
New York, NY: Oxford University Press
1999
Pg. 709 (George Bernard Shaw):
[Dancing is] a perpendicular expression of a horizontal desire.
in New Statesman 23 March 1962
 
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The Complete Idiot’s Guide to Ballroom Dancing
By Jeff Allen
Indianapolis, IN: Alpha Books
2002
Pg. 12:
After all, George Bernard Shaw said it best, “Dancing is a vertical expression of a horizontal desire.”
 
Google Books
New Contrast
South African Literary Journal,
Volume 34
2006
Pg. 5:
Someone once told me that Oscar Wilde said that dancing is a vertical expression of a horizontal desire.
 
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Wallflower in Bloom:
A Novel
By Claire Cook
New York, NY: Touchstone
2012
Pg. 172:
There was a Robert Frost quote hanging on the door of one of the practice studios that read, “Dancing is a vertical expression of a horizontal desire.”