How do you type uncommon kanji?

Prompted by my attempt to type 明治以前の穴銭 into YouTube search. Couldn’t find 銭 in the drop-down prompts after typing either あなせん　or せん and failed to come up with anything smarter than to copy the kanji from the Wiki page on Japanese coinage.

I’m using Anthy Japanese input on Linux Mint, if this is relevant.

by SpielbrecherXS