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

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

Example:

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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}
$\mathfrak{c}$