Mrs. Robertshaw begs leave to inform those ladies that found their invisible petticoats shrunk last winter that she has a kind so much improved that she will warrant them never to shrink even in the commonest wash, at the same time will be found equally as soft, pliant and warm. Everybody that has tried them allows them to be a much pleasanter article than ever before invented, being so very elastic [a word merely meaning at the time having some stretch or give] and of so beautiful a white, and, like all these comforts will add quite as little to size as her patent lambs’ wool so much approved of last winter. Likewise invisibles and stays all in one; well adapted to ladies that are confined; also under waist coats and drawers of the same description.
Of course, what makes these garments “invisible” is the fact that they’re worn between the body and the dress, hence unseen; no H. G. Wells-style trickery here. Interestingly, advertisements of this sort disappeared, so to speak, after 1816:
The year 1816 is known as the Year Without a Summer (also the Poverty Year and Eighteen Hundred and Froze To Death) because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.7–1.3 °F). This resulted in major food shortages across the Northern Hemisphere.
Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive 1815 eruption of Mount Tambora in the Dutch East Indies (now Indonesia). This eruption was the largest eruption in at least 1,300 years (after the extreme weather events of 535–536), and perhaps exacerbated by the 1814 eruption of Mayon in the Philippines.
We may perhaps assume that the tendency of women to wear less when it gets warmer goes back at least two hundred years.