A practical treatise of flowers by Peter Aram published in the 17th century
A modern edition is available at archive.org published in 1985 by the Leeds Philosophical Society
If you would have a black Gilliflower, make a Tincture of burnt Cork, Eller Cones, Charcole dust, to which add some of the best Indigo it being ye Mucilage or Sludge of a Vegetable called Nil, brought to the consistency of Paste, which is made into the form we usually see it, & in the Shops is called Fig-Indigo from its resembling ye Fruit when dryed in shape or form. If dissolved in Water, it will make a deep Tincture to be used as is directed in the Article aforegoing.
It’s clear from lots of other sources that ‘flat indigo’ is another form of the dye but I haven’t been able to find a precise description.
