It’s quite difficult to determine a species of wood from a 16th-century engraving of it.
So we don’t know for certain what sort of wood would be used to make early squares, rules and levels. One clue comes from W.L. Goodman, who wrote a two-part history of marking and measuring tools for The Woodworker magazine in 1964.
Here’s what he wrote:
“Mediaeval building accounts often refer to the purchase of old wine casks, usually made of Baltic oak or wainscot, for the carpenters to make their straight-edges, rules, and squares from this well-seasoned hardwood.”
Goodman also briefly discusses the Melencolia-type squares in the article and said they were for “setting out.”
So if you want to build some old squares, drink up!
— Christopher Schwarz