Each individual sea snail produces such a small amount of pigment that according to one study, some 10,000 were needed to produce enough secretions to dye one robe or cloak a deep shade of aptly named royal purple.
Üks tigu sisaldab väga vähe värvipigmenti. Selleks, et värvida üksainus pealisrõivas teatud tumedat tooni, mida nimetatakse kuninglikuks purpuriks, oli tarvis umbes 10 000 tigu.