“The egg piously shown
as Leda’s very own
from which Castor and Pollux hatched,
was an ostrich-egg”
“He Digesteth Harde Yron,” Partisan Review 8 (July-August 1941), 312, ll. 30-33.
“Castor and Pollux were the offspring of Leda [the wife of the king of Sparta] and the Swan, under which disguise Jupiter had concealed himself. Leda gave birth to an egg from which sprang the twins. Helen, so famous afterwards as the cause of the Trojan war, was their sister.”
Thomas Bullfinch. The Age of Fable or the Beauties of Mythology. Vol. I. New York: Review of Reviews Company, 1914, p. 158.
Moore kept a copy of The Open Court, “a monthly magazine devoted to the science of religion, the religion of science, and the extension of the religious parliament idea,” for May, 1926 (Vol. XL, No. 5). In it she read the article by Berthold Laufer on “Ostrich Egg-Shell Cups from Mesopotamia” that described the finds from a dig in Kish, Iran, sponsored by the Field Museum (Chicago) and Oxford University. The article pictured an egg-shell cup with the following description:
“The Field Museum’s loan objects include bead necklaces of semi-precious and common stones, shell, and glass, ceramic vessels, and an especially rare ostrich egg-shell cup (pictured here). All were excavated between 1923 and 1933 at the site of the ancient city of Kish in Iraq during joint archaeological expeditions by The Field Museum and Oxford University.”
The egg-shell cup pictured in the magazine has not been placed in a formal holder but is set in a simple three-legged brace. It appears that the cup was later fitted out with decorative pedestal and lid, as shown in this image from the collection of the Field Museum where it is identified as the same object as the one on page 260 of The Open Court.
On page 267 of the same article, Moore has underlined a passage from the following paragraph, clearly the source of the poem’s title:
“The fondness for metals has obtained for the bird the name of the ‘iron-eating ostrich.’ In 1579 Lyly wrote in his Euphues that ‘the estrich digesteth harde yron to preserve his health.’