DT reader and flickr user knitting iris just posted this awesome photo of her dad from before she was born, hitting Lake Louise with a kid in a tiny aluminum lawn chair strapped to his back. And a pipe.
The chair must have held up, because knitting iris herself is riding in it a few years later, and she looks pretty happy about it.
Flashback Friday [knitting iris's flickr]
That's undoubtedly not a "lawn chair" but a baby carrier. It's not dissimilar to the Kool Stop (which I own, and you wrote about in 2006), without the wheels and the fancy canopy. These things went in and out of vogue with some regularity, that is, before regulations became, well, more regular.
Note the crotch strap (in the linked image) which is not a usual feature of lawn chairs, (even if they are made for kids), the cutsey dip at the top of the back, and the shoulder straps, for wearing. Not typical lawn chair design.
Not saying you *couldn't* use it on the ground, just that it would fall over in the slightest breeze. Main use: Baby backpack.
Also, much safer than forward facing.