From Kenjutsu no Fushikihen (On Ignorance in Swordsmanship), written by Kimura Kyuhou in 1764.
The author's teacher traveled incognito and visited various schools of swordsmanship to compare systems. He said this:
"All of them employed paired kata and there were none who had achieved outstanding skill. Among those who showed little understanding were those orthodox teachers who created and taught choreographed patterns. Although it is said this makes it easy to understand and refine the principles of the style, the results should bear this out. They are unable to lead anyone to realization of the principle."
(I have yet to read the book. Quote was found on the blog: ichijoji.blogspot.com)