This was originally on Quora.com, but it was removed because they didn’t like me linking to an external website.
Give the so-called rational person a copy of Wilhelm Reich’s The Function of the Orgasm: Sex-Economic Problems of Biological Energy (The Discovery of the Orgone, Vol. 1) and explain to them that Kundalini awakening is similar in purpose and function to the release of “orgone” which Reich describes as occurring when a neurosis is abreacted.
You might also point out, however, that a traditional Yogi would view the process in far more spiritual terms than Reich would ever have countenanced: for example, a Yogi would not say neurosis so much as karma, and moreover would see the whole process as a spiritual one, whereas Reich only viewed it as a psychiatric one.