[R] Whiskers on the default boxplot {graphics}

[Jason Rupert]

How are the lower/upper whiskers defined in the default version of boxplot {graphics}?

I tried help(boxplot) and searching www.rseek.org, but I was unable to determine an absolute answer.  

I checked out the definition of boxplot according to Wikipedia (http://en.wikipedia.org/wiki/Box_plot), but it also had several approaches 
listed for how the whiskers could be determined, so I'm just curious how the default 
boxplot {graphics} does it. 

Thanks for any feedback and insights.