People are very suggestible you know. If you look powerful, they’ll assume you are powerful – in other words they’ll give you power, so their assumption is self-fulfilling. Clearly the other Rules here are important too because you don’t want to undermine your position. If everything about you comes together as a unified whole, you’ll be what you seem, and then you’ll achieve real authority.
I remember a job I did when I was about 21. I had to organize people much older and more senior than me, and get their co-operation. One day I was talking to one of them and mentioned my age. He was astounded, and couldn’t believe how young I was. He thought I was at least 30. I said, ‘Thanks a bunch. Do I really look that old?’