1647: Upside-down א in Set-Theory Jun 18, 2019

Certain letters, such as X,S,E, and B are horizontally symmetrical, but only in the right font. This may appear true of the Hebrew א, but it isn't, especially in serif-font. This would be a mostly pointless observation were it not the case that early math-books about set-theory included the Aleph—notating cardinal sets of infinity—upside-down for a long time. Some of this might be chalked up to a lack of knowledge from the printers, but also the monotype for א used in printing presses was often created upside down. See another post about א in set-theory posted today (and much more) while supporting Word Facts.