I found the following in the excellent "Now I Know" free email newsletter:

Bonus fact: In 1990, Rickey Henderson signed a five year, $8.5 million contract with the A's, which included a $1 million signing bonus.  About a year later, the A's were trying to balance their books, and kept coming up $1 million short.  The team called Henderson and asked him what he did with the check.  His answer: He put it up on his wall, uncashed, as a daily reminder that he was a millionaire.