That said, consider this *approximation* of a loose sentence from the book (the exact wording would require a specific passage, which I cannot directly quote without providing the specific book section):
"We paddled down the river, the sun beating down on our necks, the air thick with the smell of river mud and damp wood, and the cicadas singing their incessant song, until we finally reached Cairo."
This sentence starts with the main clause ("We paddled down the river") and then adds several modifying phrases describing the circumstances of the paddling. While it could be argued some of these phrases have enough weight to impact the basic meaning, the main clause stands alone and conveys the core idea. This is the key characteristic of a loose sentence.
Remember that precise classification can be subjective and dependent on interpretation. Twain's style, aiming for natural speech, often avoids perfectly structured sentences. Many sentences in *Huckleberry Finn* exhibit qualities of both loose and periodic structures, making a clear-cut "example" a matter of stylistic analysis rather than a simple definition.