How do we know that some pattern, rhythm, or meter was present in some of the Psalms? Many psalms were sung.
The first line of the Psalm states the pattern.
Many musical words and notes are used in the psalms.
Rhythm is detected when a psalm is read aloud.

Atahualpaemperor of the inca empire who rose to the throne after winning a civil war between him and his brother.  -he refused to become a spanish vassal or christian.-francisco pizarro kidnapped him and demanded a huge ransom.  -pizarro's secretary described him as "a man of thirty years, good-looking and poised, somewhat stout, with a wide, handsome, and ferocious face, and the eyes flaming with blood."-after the ransom was paid, atahualpa was killed by pizarro