“Persistent practice of postural principles promises perfection” (ballroom dancing adage)

Good posture is important in ballroom dancing. “Persistent practice of postural principles promises perfection” is a saying that has been printed in several books on ballroom dancing.
 
The authorship of the line is unknown. The saying appears to date to at least the 1960s.
 
     
the-vu
June 1, 2001
The Coast-to-Coast Meeting of the Champion Minds:
Ron Montez and Dan Radler
By Kim Knode
(...)
To improve the chances of high marks, when the adjudicator is glancing at a pair of dancers, Radler reminds his protégées that, “Persistent practice of postural principles promises perfection.” The New Englander reiterates (what my statuesque aunt always told me as an adolescent): “Good posture makes you look elegant and exude confidence.”
 
Dance Reality
Sunday, March 20, 2005
How judges judge us?
I would like to attempt to answer an often-asked question of interest to both spectators and competitors at dance competitions: What factors does a judge weigh in assessing a couples performance?
(...)
POSTURE - one of the most important aspects. Good posture makes you look elegant and exude confidence. It improves balance and control, and allows your partner to connect well to your body in the smooth dances. One’s competition result is often directly proportional to one’s postural correctness. Hence the old adage, “Persistent practice of postural principles promises perfection.”
 
Google Books
Ballroom Dancing:
Learn Romantic Ballroom Dance Steps & Types of Dance to Ignite the Passion
By Desiree Victoria Carey
Lulu Press, Inc. (Lulu.com)
2013
Pg. ?:
The old adage is “Persistent practice of postural principles promises perfection” gives you a clue to the importance of good posture in any ballroom dance.
   
A Step To Gold (International Ballroom)
Could I Compete?
Posted by Melanie on March 30, 2015
(...)
Posture: Have you ever heard of the old adage “Persistent practice of postural principles promises perfection”? Good posture allows for better balance and control, making this point equally part of show and function.
   
The Irish Times
The Times We Lived In: Dancing out of step with the Dáil on neutrality
Published: May 11th, 1967 Photograph by Eddie Kelly
Arminta Wallace
Sat, Jun 27, 2015, 00:00
‘Good posture makes you look elegant and exude confidence,” the ballroom dancing rule-book declares. “Hence the old adage, ‘Persistent practice of postural principles promises perfection’.” The same might be said (if you can say it without stumbling) of politics.