`_`	(the underscore) is the placeholder for exactly one character.
`%`	(the percent sign) is the placeholder for no, one or more than one character.
`%%`	(two percent signs) is the placeholder for no, one or more than one character, but not for blank space (so that a search ends at word boundaries).

Federico Commandino, In Planisphaerium Ptolemaei commentarius

Venice, Paulus Manutius Aldi, 1558 · 18v

Sit pyramis basim habens ABC verticem D, cuius altitudo linea DH. Sit autem dicta pyramis vel ultra datum planum, vel citra, vel partim ultra, partim citra. Itaque describantur

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