<A HREF="https://en.wikipedia.org/wiki/Charles_Sanders_Peirce">Charles Sanders Peirce</A> is credited with the "beth" ℶ notation, in a December 1900 letter to Cantor.

[![enter image description here][1]][1]    
[![enter image description here][2]][2]

<A HREF="https://www.jstor.org/stable/41302100">[source]</A>


  [1]: https://i.sstatic.net/ejfKA.png
  [2]: https://i.sstatic.net/qpKKb.png