What is Baculus?

Legal Definition
A rod, staff or wand, used in old English practice in making livery of seisin where no building stood on the land, (Bract. 40;) a stick or wand, by the erection of which on the land involved in a real action the defendant was summoned to put in his appearance; this was called "baculus nuntiatorius." 3 Bl. Comm. 279.
-- Black's Law Dictionary
Legal Definition
A divining rod; a rod used in making livery of seisin.
-- Ballentine's Law Dictionary