Lea's been sitting unassisted for a couple of minutes at a time for about ten or so days now, but now she seems to have mastered the skill sufficiently to allow me time to grab the camera and take a shot of her in action without fear of her toppling over and hurting herself.
On an unrelated matter, it seems that kids who are not on oxygen and have their own always-at-the-ready nasal canula upon which to hold are at a real disadvantage relative to their oxygen-dependent counterparts. Hallie always used her canula as a security blanket, of sorts. Here's a picture of Hallie at about 4 months (corrected) holding her love object:
Lea had to go and find a hula hoop to grasp to derive the same pleasure.