When they are real, they are not glass threads or frostwork, but the solidest thing we know.
"Essays, First Series" by Ralph Waldo Emerson
Frostwork is something too delicate for human hands, but in it we excel.
"Prince Lazybones and Other Stories" by Mrs. W. J. Hays
And that lace is as delicate as frostwork!
"The Court Jester" by Cornelia Baker