How does one use the Old English fonts? e.g. for ring ideals

Question

I'd like the Old English fonts used for ideals, cardinality of the reals, etc.

Example:

Answer 1

I think the usual method is to use the Fraktur font (strictly speaking, not Old English, but a Germanic gothic font, but close) provided by, e.g., amsfonts:

\documentclass{article}
\usepackage{amsfonts}
\begin{document}
     $\mathfrak{c}$
\end{document}

The yfonts package provides some interesting alternatives you may wish to look at too.