This watercolour plate is taken from the album Monuments mégalithiques du Département de la Vienne, made by Le Touzé de Longuemar, a correspondent of the Commission de Topographie des Gaules (CTG). The illustration is a suggestion for how dolmens may have been erected. The size of the stone blocks particularly intrigued 19^th-century archaeologists. This study, accompanied by detailed notes, shows the engagement of CTG correspondents in the analysis of remains in their region.