(Radio.com) Muhammad Ali, a three-time world heavyweight boxing champion and cultural icon, died at age 74 after a brief hospitalization, a spokesman confirmed early Saturday, according to CBS News.

A number of musicians took to Twitter to pay their respect, including Usher, and Paul McCartney (who shared an iconic photo of the Beatles with the champ). McCartney said, via his website, that "Besides being the greatest boxer, he was a beautiful, gentle man with a great sense of humour who would often pull a pack of cards out of his pocket, no matter how posh the occasion, and do a card trick for you. The world has lost a truly great man."

As McCartney said, Ali was more than just a boxer; although he was a three time champion of the world, he also transcended his sport. Muhammad Ali was a pop culture phenomenon who brought a form of poetry to the boxing ring: his interviews were as lyrical as some of the best popular music. His "Float like a butterfly, sting like a bee" line has become part of the pop culture lexicon. See some of the other tributes here.

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