A Review of Buffet's Partnership Letters here.

From it :
There is some ambiguity in the statements he makes now and the way that he ran his business back then. He talks about how he never used margin but he actually did. Sometimes he would borrow up to 25%. He also berates fund managers for the fees they charge but his funds charged 25% of anything over 6%. He also had other fee schedules that would charge 1/3 of all profits (with no bogey). These high fees are where he made his original wealth that would allow him to be the largest shareholder of his current company and one of the wealthiest people in the world.