The colour purple was reserved only for the emperor and senators, and any flaunting it was a betrayal. This dye was obtained from spike venom (Murex).
It was the so-called “Tyrian purple” and was the only known source of an intense purple colour until the 16th century (though, of course, attempts were made to counterfeit it in various ways), and dyeing a kilogram of fabric, it was calculated, required to catch and “remake” about 10 thousand snails.
The cost of real Tyrian purple is enormous to this day – for 5 grams of the dye you have to pay about 2,000 PLN.
