The use of poetry in non-fiction books such as history, biography or religion as a reference was common during the late 19th and early 20th centuries. Snippets of poetry verses pertaining to a certain idea presented in the actual text – or even a footnote – was artistic as well as aesthetic. Longer sections of verse might also be used within the too, as in the following example where a poem by Lord Byron is used to describe Rousseau in “The Confessions” (London: Aldus Society, 1903):
Lord Byron had a soul near akin to Rousseau’s, whose writings naturally made a deep impression on the poet’s mind, and probably had an influence on his conduct and modes of thought: In some stanzas of ‘Childe Harold’ this sympathy is expressed with truth and power; especially is the weakness of the Swiss philosopher’s character summed up in the following admirable lines:
“Here the self-torturing sophist, wild Rousseau,
The apostle of affliction, he who threw
Enchantment over passion, and from woe
Wrung overwhelming eloquence, first drew
The breath which made him wretched; yet he knew
How to make madness beautiful, and cast
O’er erring deeds and thoughts a heavenly hue
Of words, like sunbeams, dazzling as they passed
The eyes, which o’er them shed tears feelingly and fast.
“His life was one long war with self-sought foes,
Or friends by him self-banished; for his mind
Had grown Suspicion’s sanctuary, and chose,
For its own cruel sacrifice, the kind,
‘Gainst whom he raged with fury strange and blind.
But he was frenzied,—wherefore, who may know?
Since cause might be which skill could never find;
But he was frenzied by disease or woe
To that worst pitch of all, which wears a reasoning show.”
Here is an example of a poetry verse appearing in with main text of a history book (from “Prince Henry the Navigator: The Hero of Portugal and of Modern Discovery” by C. Raymond Beazley, M.A., F.R.G.S. New York: G. P. Putnam’s Sons, 1895):
On the south and south-west no Vikings or Royalist followers of Vikings, like Sigurd the Crusader, sailed the seas beyond Norva’s Sound and Serkland, and as pilgrims, traders, travellers, and conquerors in the Mediterranean, their work was of course not one of exploration. They bore a foremost share in breaking down the Moslem incubus on southern Europe; they visited the Holy sites[Pg 67]
“When sacred Hierosolyma they’d relievèd
And fed their eyes on Jordan’s holy flood
Which the dear body of Lord God had lavèd”;
 Camoëns, Lusiads, (Barton’s trans.).
Or a poetry verse might appear in the footnote, from the same book:
Failing to take the sea route at Ormuz for China, as they had hoped, our Italians were obliged to strike back north-east, through Persia and the Pamir, the Kashgar district and the Gobi steppes, to Cathay and the pleasure domes of Kublai, visiting Caracorum and the Altai country on the way, by a turn due north. In 1275 they were in Shang-tu, the Xanadu of Coleridge—the summer capital of Kublai Khan—and not till 1292 did they get leave to turn their faces to the West once more.
And the footnote:
 In Xanadu did Kublai Khan
A stately pleasure-dome decree,
Where Alph, the sacred river, ran,
Through caverns measureless to man,
Down to a sacred sea.
This style of blending verse in with nonfiction is not confined to print publishing of yesteryear. A modern example would be like the following article I wrote for HubPages:
What makes the Scorpion a real challenge to identify is his voice, which belongs to none of the unmasked characters in the story. Instead, actor Gerald Mohr (who later did voice-overs in the Hanna-Barbera cartoon “The Fantastic Four”) loaned his sinister-sounding voice as Captain Marvel’s adversary while one of the members of the archaeological expedition posed in front of the camera in his black Scorpion hooded mask and robe. There is one point in the serial where Captain Marvel chases the Scorpion through a network underground, and the Scorpion’s hood comes off but the shadows conceal his true identity, right up until the very end. Thus the Scorpion’s quest for world power comes to an end, per Edwin Arnold:
We are the voices of the wandering wind,
Which moan for rest and rest can never find.
“The Adventures of Captain Marvel” holds the viewer spellbound with its plot turns, top notch acting, special effects, and cliffhangers at the end of each chapter, designed to encourage the continued watching of the serial.
When writing a nonfiction piece and poetry is desired as a reference somewhere in the text, use a website like Poemhunter.com to locate the subject you are writing about, and the verses you want to use. Do not forget to include the poet’s name somewhere next to the poetry reference.