Saffron, botanical name crocus sativus, is the most expensive spice in the world. Derived from the dried stigmas of the purple saffron crocus, it takes anything from 70,000 to 250,000 flowers to make one pound of saffron. Moreover, the flowers have to be individually hand-picked in the autumn when fully open. Fortunately, only a little needs to be added to a dish to lend it colour and aroma; too much makes the food bitter and as the quotation from Culpeper (below) suggests, large quantities of it can be toxic.

'The use of it ought to be moderate and reasonable, for when the dose is too large, it produces a heaviness of the head and sleepiness. Some have fallen into an immoderate convulsive laughter which ended in death.'
Culpeper's The Complete Herbal, 1649