This line, and indeed the whole passage (lines 653-664), allude to the well-known poem by Goethe about the erlking, hoary enchanter of the elf-haunted alderwood, who falls in love with the delicate little boy of a belated traveler.

At one time a standard test for carriage riding was to stand a pencil on end on the compartment floor, or to measure how long it was possible to stand on one leg without touching the corridor walls; ….

The Irish cloak forms very graceful drapery; the material falls well, and folds well. It is usually large enough to envelop the whole person; and the hood is frequently drawn forward to shield the face of the wearer from sun, rain, or wind. Yet we would fain see its general use dispensed with. A female in the lower ranks of life cares but little for the other portions of her dress if she has a good cloak; and certainly her ordinary appearance would be more thought of, if the huge cover-slut were not always at hand to hide dilapidations in her other garments.

I told him what I had done, how I had counted coup in a Pottawattomie, and he shook hands and said that he too had counted coup and that he was going to wear a head ornament.