I knew the Shakespearean version of the assassination of Julius Caesar, which occurred on the Ides of March in 44 BC, but there's a lot more to it than that, according to this report.
Spurinna was a haruspex. His calling was vital, if a little unusual, requiring him to see the future in the warm entrails of sacrificial animals.
At the great festival of Lupercalia on the 15th of February 44 B.C., he was a worried man. While priests were running around the Palatine Hill hitting women with thongs to make them fertile, Spurinna was chewing over a terrible omen.
The bull that Julius Caesar, Dictator of Rome, had sacrificed earlier that day had no heart. Spurinna knew it was a terrible sign: a sure portent of death.
The following day, the haruspex oversaw another sacrifice in the hope it would give cause for optimism, but it was just as bad: the animal had a malformed liver. There was nothing for it but to tell Caesar.
In grave tones, Spurinna warned the dictator that his life would be in danger for a period of 30 days, which would expire on the 15th of March. Caesar dismissed the concerns. Although in his scramble for political power he had been made the chief priest of Rome (Pontifex Maximus), he was a campaign soldier by trade, and not bothered by the divinatory handwringing of seers like Spurinna.
As the 30 days passed, nothing whatsoever happened. Yet when the 15th of March dawned, Caesar’s wife awoke distressed after dreaming she held his bloodied body. Fearing for his life, she begged him not to leave the house. His dreams, too, had also been unsettling. He had been flying through the air, and shaken hands with Jupiter. But he pushed any concerns aside. The day was an important annual celebration in Rome’s religious calendar, and he had called a special meeting of the Senate.
His first appointment of the day was a quick sacrifice at a friend’s house. Spurinna the seer was also there. Caesar joked that his prophecies must be off as nothing had happened. Spurinna muttered that the day was not yet over.
There's more at the link.
Of course, much of what's come down to us as history was written by the 'victors' in this little affair, so I don't know how much credence to place in it. Certainly, I don't go with the account of the haruspex above: after all, a bull born without a heart couldn't live long enough to grow to adulthood and be sacrificed, so that's a non-starter, right there! Even so, there's clearly a lot more to the tale of Julius Caesar's assassination than Shakespeare included in his famous play. Interesting stuff.