This nonation appears on Partite diverse sopra l'Aria 'Schweiget mir von Weiber nehmen' by Reincken, Johann Adam, IMSLP #04945.
The Dolmetsch Musical Symbols guide lists the = symbol, but not ≡, but for = it says this:
a symbol found above note heads in The Bird Fancyer's Delight which is explained in the original publication thus: "The marks & rules for graceing are these Viz. a close shake thus ="
I expect that you'd perform = similarly to ≡