When was the beach blanket invented?

Looking at those woolen dresses covered in sand is giving me a case of the hives. I don't even want to imagine how heavy and uncomfortable those clothes were when they got wet. I had to feel like chain mail. For those who stayed out of the water, it was probably tolerable, since they would be wearing lighter fabrics, but the swimming costumes were all wool, I believe. Brave ladies. I'd have stayed on the shore.

I'm guessing these same people would picnic on a nice park lawn or meadow and put a blanket down first thing. Why not on yucky hot sand?

but not one person brought a blanket or towel to sit on. Strange.

Apparently this was before anyone thought to bring a towel to spread on the beach sand. Looks more like a mud fight than a beach scene.