to sit light and erect

The clear-eyed girl, sitting light and erect on the couch.
What does to sit light and erect mean?

beachboy said:

The clear-eyed girl, sitting light and erect on the couch.
What does to sit light and erect mean?

Click to expand...

Sitting "light" means she was just gently seated on the sofa, perhaps towards the front edge. She wasn't fully squashed up on it, looking very comfortable and snug.

Sitting "erect" means she was sitting very upright, her spine was very straight.

beachboy said:

The clear-eyed girl, sitting light and erect on the couch.
What does to sit light and erect mean?

Click to expand...

Beachboy, imagine yourself sitting on a couch while watching a soccer game on TV. I bet you would not be 'sitting light and erect'. You would be comfortably sprawled-out while snacking on your favorite food and beverage! You probably would not want to invite the 'clear-eyed girl sitting light and erect' to watch the game with you!