Collections: Clothing, How Did They Make It? Part IVa: Dyed in the Wool – A Collection of Unmitigated Pedantry
https://acoup.blog/2021/04/02/collections-clothing-how-did-they-make-it-part-iva-dyed-in-the-wool/Indigofera tinctoria - Wikipedia
https://en.wikipedia.org/wiki/Indigofera_tinctoria