This fun riddle was first published in the 1921 book Children’s Literature, A Textbook of Sources for Teachers and Teacher-Training Classes written by Charles Madison Curry and Erle Elsworth Clippinger.
Riddle:
In marble walls as white as milk,
Lined with a skin as soft as silk,
Within a fountain crystal clear,
A golden apple doth appear.
No doors there are to this stronghold,
Yet thieves break in and steal the gold.
(click on the riddle to find out the answer)
Answer: An Egg.