HARRY "HAYWIRE MAC" McCLINTOCK (the great), in an interview with SAM ESKIN, folklorist, on a wonderful Folkways LP, tells how and when he WROTE "Big Rock Candy Mountain". He sings the song on that recording but says that the original he'd first written was pretty "adult". He goes on to say (sadly) that some hobos used the story of the fantastic mountain to lure young boys onto the road with them to do work for them "among other things"!
As far as I know the original is lost! Thankfully!