It's not in the Opies' book of nursery rhymes, oddly enough; but it is included in Baring-Gould, The Annotated Mother Goose, #872:

Up and down the City Road,
In and out of the Eagle,
That's the way the money goes,
Pop goes the weasel!

Half a pound of tuppenny rice,
Half a pound of treacle,
Mix it up and make it nice,
Pop goes the weasel!

Every night when I go out
The monkey's on the table;
Take a stick and knock it off,
Pop goes the weasel!

They translate *treacle* as "molasses", and explain the weasel as a cobbler's tool of some sort, which would be *popped* or pawned on a Friday to get the money to go up and down the road and in and out the pub. [The word, BTW, is not in the Oxford Dictionary.] That third stanza I don't know; maybe we should get other folks' versions, like Bert's Cotton road etc.I mean, we might find an American [or Transatlantic] version of its own.[RG!! where did you get yours??] There are a few versions in the DT, the Scottish ones contributed by me.-- in which the "theevil" is a stick for stirring porridge.