Funny you mention Hill. In his 'Your Right To Be Rich' he states that "personal magnetism" (direct synonym of charisma, in my mind) is "...an inborn trait..." the only one of the 25 traits of a pleasing personality that "cannot be cultivated
, but it can be controled and directed to benefitial uses."
Hill also mentions a "reference to the sexy motion" when discussing this, though I don't quite get the link. In Think and Grow Rich, he talks about sex transmutation which is transferring sexual energy into other things as Ghandi or Hitler may have, but I don't understand what that has to do with the trait of Charisma specifically.
Anyway... just thought I'd share. I'm not sure what my own personal opinion on charisma is. Just that I wish I had more of it!