I intended an ode,
And it turned to a sonnet.”
This may be better rhyme, but the raison d’être is gone; it has not turned to a sonnet, but is still a triolet.
To understand the form more clearly, it is best to take one and dissect it, thereby showing its structure. To avoid mutilating a master’s work, and possibly misinterpreting it, I will take one in my possession, not yet published, printing it, not as it would be, but displayed (to use a technical term), thereby exaggerating the emphasis with which the writer intended it should be read.
“A Waverer.
She has a primrose at her breast:
I almost wish I were a Tory.
I like the Radicals the best,
SHE has a primrose at HER breast,
Now is it chance she so is drest?