The signatures on the handwritten note belonged to Williams, John Henry Williams and Claudia Williams.
Bobby-Jo Ferrell, Williams' eldest daughter and half-sister to John Henry and Claudia, has contended since his death July 5 that he wanted to be cremated with his ashes scattered over his old fishing waters in the Florida Keys.
A will dated in 1996 was filed with probate court July 16, and said he wanted to be cremated. But the new note carries a more recent date of Nov. 2, 2000, a day on which Williams underwent surgery at Shands Hospital in Gainesville, Fla.
Ferrell has not responded to the new note, but a court battle over the issue is still expected.
The note reads: "John, Claudia and Dad all agree to be put into bio-stasis after we die. This is what we want, to be able to be together in the future, even if it is only a chance."
Bob Goldman, lawyer for John Henry and Claudia, said they wanted to keep it private, but weren't able to do that because of Ferrell. He said the privacy issue was the reason the existence of the note was not revealed until Thursday.
In a written statement, Claudia and John Henry Williams said, "With relief, we have provided the court with clear-cut definitive evidence that our father's last wishes have been carried out and we hope this will bring closure to this issue."
They also released a photograph of the note.
Williams, considered one of the best hitters in the history of baseball if not the best, died of cardiac arrest at the age of 83 after years of heart trouble and a serious stroke.
Ferrell said that hours after his death, her father's body was sent to Alcor Life Extension Foundation in Scottsdale, where it was frozen at minus 320 degrees Farenheit so it could be revived later.
She said John Henry Williams hopes to sell Williams' DNA or profit some other way from his fame. But Jerry Lemler, director of Alcor said many of the schemes that have been mentioned aren't possible, especially if they involve cloning. He said Williams' DNA had been readily available by using strands of hair or fingernail clippings.