looking for the name of a sci-fi short story, 1980's or before. the plot is somewhat like:
father gives kids odd object to play with. the kids play with the object. kids discover 4th of 5th dimension and disappear. father spends rest of his life trying to figure out the object. a quote is from father asking one the children about some pretty view or object and child answers to the effect of "it's not quite right".