The ancients used yarrow stalks to perform divination.
Tips
history
蓍 is not used alone in modern Chinese; it lives on in 蓍草 ('yarrow') and the classical pairing 蓍龟 ('yarrow stalks and tortoise shell', the two ancient methods of divination). The grass radical 艹 marks the plant; 耆 supplies the sound.
culture
Bundles of 蓍 stalks were the casting tool of the 《易经》, sorted by hand to build a hexagram, hence its weight in classical thought.