Purple was an absurd luxury. A drop of secretion from a sea snail's hypobranchial gland, spread on cloth and exposed to air and sunlight, could pass from pale fluid to violet and then a dark, lasting hue. The odor was brutal. Its visual force survived washing and wear, making the stench a tolerable entry fee.The price was no accident. The gland produced only a minute supply of tyrindoxyl sulfate, ...More