The menhir is a block of almost rectangular sandstone. It is 2.40 m high, 1.40 m wide and 0.70 m thick on average. Its presence hinders the exploitation of a sandpit, it was shot around 1911-1912 and then straightened after backfilling of it at the end of the activity.
The menhir is reported as early as the eighteenth century. It is mentioned in several acts of the abbey of Saint-Germain-l’Auxerrois under various denominations: Pierre de Monceau, Big Stone, Big Caillou, Brush Bourne, Bourne.
The name “Mousseau” or “Montceau” probably corresponds to the ancient existence of a tumulus nearby.
It was discovered in 1875 during the exploitation of the sandpit. The owner of the land Jean-Baptiste Piketty searched the site. It presented itself as an oval pit (7 m long by 3 m wide), 2 m deep, surrounded by a dry stone wall. It did not have a blanket. According to the authors, the description of the interior of the tomb is variable: according to some, the ground was paved with limestone flat stones (Ph.Salmon) and the pit contained the remains of about forty individuals lying in disorder ( JB Piketty), for others, the ground was covered with millstone blocks (Adrien de Mortillet) and the bodies were aligned in two rows (F. Martin).
The archaeological material collected, mainly by Piketty in 1875, consists of: