Muhammad Ali poses with gloves in this undated early portrait. Action Images / Sporting Pictures/ via Reuters

Heavyweight champion Muhammad Ali was momentarily displeased after the weigh-in ceremony on May 25, 1965, in Lewiston, Maine, when he boxed Sonny Liston. Liston weighed 215¼ pounds and Ali weighed 206.

Heavyweight champion Muhammad Ali stands over fallen challenger Sonny Liston in the first round of their title fight in Lewiston 50 years ago.

Promoter Don King stands between Muhammad Ali, left, the heavyweight champion, and Joe Frazier in New York, Thursday, July 17, 1975, after it was announced that Ali and Frazier will meet in a title bout. The Associated Press

Muhammad Ali lights the Olympic flame during the 1996 Summer Olympic Games opening ceremony in Atlanta. At right is U.S. swimmer Janet Evans.

U.S. boxing great Muhammad Ali poses during the Crystal Award ceremony at the World Economic Forum in Davos, Switzerland, Jan. 28, 2006. Reuters

Muhammad Ali, former world heavyweight boxing champion, toys with the finely combed hair of television sports commentator Howard Cosell before the start of the Olympic boxing trials in West Point, N.Y.

Heavyweight champion Muhammad Ali connects with a right to challenger Joe Frazier in the ninth round of their title fight in Manila, Philippines, on Oct. 1, 1975. It was, Muhammad Ali would later say, the closest thing to death he had ever known. He and Frazier had gone 14 brutal rounds in stifling heat before Frazier's trainer Eddie Futch mercifully signaled things to an end, his fighter blind and battered and feeling pretty close to death himself. The "Thrilla in Manilla’’ still lives in sporting lore.

Muhammad Ali is held back by referee Joe Walcott, left, after Ali knocked out challenger Sonny Liston in the first round of their title fight in Lewiston. The Associated Press

Young heavyweight boxer Cassius Clay, who later changed his name to Muhammad Ali, points to a sign he wrote on a chalk board in his dressing room before his fight against Archie Moore in Los Angeles, predicting he'd knock Moore out in the fourth round, which he went on to do. The sign also predicts Clay will be the next champ via a knockout over Sonny Liston in eight rounds. He did it in seven rounds.

World heavyweight boxing champion Muhammad Ali, right, is shown with Nation of Islam leader Malcolm X outside the Trans-Lux Newsreel Theater on Broadway in New York City on March 1, 1964. They had just watched a screening of films on Ali's title fight with Sonny Liston in Miami Beach.

Muhammad Ali puts on a show at the New York State Athletic Commission's office in New York City on Jan. 23, 1974, as he tries to force his way into the room where Joe Frazier was getting his pre-fight physical.

Heavyweight boxing champion Larry Holmes and boxing promoter Don King laugh as Muhammad Ali snarls at Holmes during a joint press conference at Caesars Palace in Las Vegas on Oct. 3, 1980. Holmes successfully defended his title against Ali when Ali failed to answer the bell for the 11th round.

Joe Frazier, right, slugs it out with Muhammad Ali during a fight at Madison Square Garden – the second of their three fights. Frazier won the first, then lost the next two.

Heavyweight champion Muhammad Ali leans on the ropes after he successfully defended his title against Earnie Shavers at New York's Madison Square Garden on Sept. 29, 1977. Ali was awarded an unanimous decision in the fifteen-round fight with Shavers.

Muhammad Ali works out before his bout against George Foreman in October 1974.

Muhammad Ali wipes sweat off his face after a 10-round workout at a gym in Congo on Oct. 18, 1974.

World heavyweight boxing champion Muhammad Ali is shown trying to evade kicks by wrestler Antonio Inoki during their 15-round World Martial Arts match in Tokyo.

President George W. Bush presents the Presidential Medal of Freedom to boxer Muhammad Ali in the East Room of the White House.

A trio of U.S. boxers, including Cassius Clay, wear gold medals at the Olympic village in Rome, in this Sept. 6, 1960 photo. From left are: Wilbert McClure of Toledo, Ohio, light middleweight; Cassius Clay of Louisville, the future Muhammad Ali, light heavyweight; and Edward Crook of Fort Campbell, Ky, middleweight. The Associated Press

Former heavyweight boxing champion Muhammad Ali is crowned “King of Boxing” while accompanied by his wife, Lonnie, right, and Argentine boxer Sergio Martinez during the 50th convention of the World Boxing Council in Cancun, Mexico.

Muhammad Ali, with the support of sister in-law Marilyn Williams, left, and wife Lonnie, walks through the Muhammad Ali Parkinson Center at Barrow Neurological Institute at St. Joseph's in Phoenix. Ali has suffered from advanced Parkinson’s – a degenerative disease he’s lived with for three decades.

Muhammad Ali knocks down George Foreman.

Men pass a large sign by an escalator near the entrance of the "I Am The Greatest, Muhammad Ali" exhibition at the O2 arena, which hosts high profile boxing fights in London, on Saturday. The Associated Press

In this Sept. 18, 1975, photo, Philippines President Ferdinand Marcos, left, applauds as challenger Joe Frazier makes some remarks about world champion Muhammad Ali. The Associated Press

Large posters of mostly Sports Illustrated magazine covers are displayed at the "I Am The Greatest, Muhammad Ali" exhibition at the O2 arena, which hosts high profile boxing fights in London, The Associated Press

A huge billboard heralding the epic 1975 "Thrilla in Manila" heavyweight boxing bout between Muhammad Ali and Joe Frazier dominates the entrance at the exact venue 40 years ago at the Araneta Coliseum which is now renamed as Smart Araneta Coliseum in Cubao. The Associated Press

In this July 17, 2011 photo a sculpture depicting former president Nelson Mandela as an amateur boxer in his youth, by artist Des Khoury is displayed at an Arts and Antiques Fare in Johannesburg. On the passing of Muhammed Ali. The Associated Press

Staff members walk past a boxing glove with the autograph of Muhammad Ali and his handprint displayed at Korakuen Hall, the main venue for major boxing matches, in Tokyo . The Associated Press

In this Dec. 20, 1978, photo, world heavyweight champion Muhammad Ali carries his daughters, 2-year-old Hana, left, and nine-month-old Laya at London's Heathrow Airport. The Associated Press

In this March 17, 1966, photo, heavyweight boxing champ Muhammad Ali, or Cassius Clay at the time, paused on the step and greeted a friend, as he arrived at the Veterans building to appeal his 1A draft classification. Behind him, dark coat and hat, is his attorney, Edward Jocko of New York. The Associated Press

In these Nov. 29, 1974, photos combo, World Heavyweight Boxing Champion Muhammad Ali reacts while speaking at a press conference in London. The Associated Press

In this Sept. 10, 1974, photo, a Zairian man in traditional clothing carries a spear as he leads Muhammad Ali through a crowd at the airport in Kinshasa, Zaire. The Associated Press

US-American boxer Cassius Clay (later Muhammad Ali), with his first wife, Sonja, on Sept. 19, 1964. The Associated Press

In this July 1984 photo, former heavyweight champion Muhammad Ali carries the Olympic torch into the stadium in Los Angeles. The Associated Press

In this March 1, 1964, photo, world heavyweight boxing champion Cassius Clay (Muhammad Ali) signs autographs outside the Trans-Lux Theater on Broadway at 49th Street in New York City. Standing behind Ali is Malcolm X. The Associated Press

In this Sept. 27, 2014, photo, back row, from left, John Wooten, Jim Brown, Bill Russell, and Bobby Mitchell stand behind Muhammad Ali before the start of the Ali Humanitarian Awards ceremony in Louisville, Ky. The Associated Press

In this July 19, 1996, photo, American swimmer Janet Evans looks on as Muhammad Ali lights the Olympic flame during the 1996 Summer Olympic Games opening ceremony in Atlanta.

In this Aug. 5, 1966, photo, heavyweight boxer Muhammad Ali, right, visits Cleveland Browns running back and actor Jim Brown on the film set of "The Dirty Dozen" at Morkyate, Bedfordshire, England.

In this photo, boxing legend Muhammad Ali holds up the first Olympic torch lit from the cauldron in front of a map showing the torch's route during a ceremony at Centennial Olympic Park in Atlanta. The Associated Press

In this Dec. 17, 2005, photo, Muhammad Ali, left, looks to his daughter Laila after she won a non-title fight against Asa Maria Sandell from Sweden, in Berlin, Germany. The Associated Press

In this Feb. 18, 1964, photo, the Beatles, from left, Paul McCartney, John Lennon, Ringo Starr, and George Harrison, take a fake blow from Cassius Clay (Muhammad Ali) while visiting the heavyweight contender at his training camp in Miami Beach, Fla. . The Associated Press

Joel Valero lights a candle at an impromptu memorial for Muhammad Ali outside the Scottsdale Osborn Medical Center on Saturday in Scottsdale, Ariz. The Associated Press

Toni Ingraham struggles with her balloons in the breeze before placing them on an impromptu memorial for Muhammad Ali outside the Scottsdale Osborn Medical Center on Saturday at Scottsdale, Ariz. The Associated Press

Mike Ingraham ties balloons on an impromptu memorial for Muhammad Ali outside the Scottsdale Osborn Medical Center, Saturday in Scottsdale, Ariz. The Associated Press

In this Oct. 2, 1980 photo, World heavyweight champion Larry Holmes, left, pounds challenger Muhammad Ali in the corner during championship fight in Las Vegas, Nev. Holmes won when Ali failed to answer the bell to start the 11th round. The Associated Press

In this Sept. 28, 1976, photo, challenger Ken Norton, left, and heavyweight champion Muhammad Ali trade right punches in the late rounds of their title fight in New York's Yankee Stadium. . The Associated Press

A man walks along 125th street passing the Apollo Theater marquee that carried a tribute to Muhammad Ali on Saturday. The Associated Press

Muhammad Ali accepts the President's Award accompanied by his wife Yolanda Williams at the 40th Annual NAACP Image Awards at the Shrine auditorium in Los Angeles February 12, 2009. REUTERS/Mario Anzuoni (UNITED STATES) - RTXBKME