A childrens misquote?

Shakespeare's famous 1606 play, Macbeth, featured the 3 witches who's various prophesies to him included the message that he shall be king. They were best known for this, and the spells they cast as they tossed various horrible artifacts into their cauldon.

But many people recall this as either "Hubble, bubble" or various combinations such as "Hubble, hubble" or "Bubble, bubble" etc - none of which contain the word "double". Is this a Mandela Eeffect or just a misquote from children seeing the scary witches and associating the phrase with the sound their big black cauldron makes?

Double, double toil and trouble;
Fire burn and cauldron bubble

Macbeth

The full title is The Tragedy of Macbeth and is a lasting insight into the damaging effects those who seek power for it's own sake cause. It's as relevant today as it was back in 1606, when it was first performed, and is Shakespeare's shortest tragedy.

It's also famous in theatres for the widespread idea that the play is cursed, and many back stage will not speak the title aloud, preferring instead to refer to it as "The Scottish Play". A staple of many theatres throughout the 4 centuries since it was written, it has seen the best, most famous acting talent the world has had to offer in performances, and been adapted many times to film, TV, opera as well as being an often thinly-disguised basis for many other stories.

The suspicion of witchcraft was prevalent at the time of writing, and The North Berwick Witch Trials had only taken place around 10 years before it was written in 1590. Shakespeare is known to have a keen eye for exciting his audience with ideas and places which would have been exotic and unknown to them at the time. This can be seen in his other plays, such as casting The Merchant of Venice in Italy, for example. His typical audience wasn't like today where a mouse click could update you on anything you wanted to know more of, he knew full well he was the equivalent of the TV, books and news all rolled into one when it came to their entertainment.

So when the Spell "double, double" came up, and indeed the very idea of the witches, it would have had seemed to be particularly closer to home to his audience of the day than to us.