Check the video near the top of this page:
http://ruina.tam.cornell.edu/researc..._and_links.htm

Direct link:
http://ruina.tam.cornell.edu/researc..._stability.mov

Even so, I still can't ride no-handed. I couldn't do it as a little kid, either. I've had moments when I was able to stay straight for several seconds, but that's it. I have NO idea what I'm doing wrong, but I also don't care enough about it to work on it.