This is such a beautiful GIF.
Charles L. "Sonny" Liston ( c. 1930 – c. December 30, 1970) was an American heavyweight pro boxer who competed from 1953 to 1970.
Here's a super interesting archival interview with Liston about how he got his start in boxing — at 13 years old.
Some really interesting observations about when you know you've got it.
[photo: Florida Memory, 'Championship fight between Cassius Clay and Sonny Liston: Miami Beach, Florida' Local call number: RC11106 Date: February 25, 1964, No known copyright restrictions]