Wonder whether any of you know where it was that the following pearl of topology first appeared:

> Prove that at any instant of time you can find three isothermal points on the surface of the Earth that correspond to the vertices of an equilateral triangle.

According to [Léo Sauvé][1], all problems appeared once in the *Monthly*. Does that *dictum* apply to the above teaser, too?

  [1]: https://mathoverflow.net/questions/145475/what-is-the-source-of-this-erdos-quote