The earliest surviving epitaphs or commemeorative inscriptions date back to Egyptian sarcophagi, ancient Greek epitaphs were often of literary interest. Selecting a verse for a memorial can take many forms, from traditional scripture to poetry to a familiar family phrase.
On an island far to the west, beyond the edges of the map lies the land of Tir na nOg. Taken from Irish legends, tis the land of eternal youth, land of the ever young.
"Like sheaves of corn, he gathers you unto himself." A line of poetry from Khalil Gibran, perhaps best remembered for his work, The Prophet. 26 poetic essays ranging from love and marriage, to religion and prayer
The opening line of the 43rd of the 44 Sonnets from the Portugeuse by Elizabeth Barrett Browning, who wrote in secret about her husband to be, poet Robert Browning.
From the book of Psalms,
to the 117 verse, Songs of Solomon
As you can see, there is no set rule about verses, today's families chose to express their feelings about their loved ones in a variety of ways.