The thermic bottle (A131) is a classic sensorial material used to develop the child's ability to discriminate temperature through touch alone, typically introduced in the 3–6 environment as part of the broader sensorial sequence. Filled with water at varying temperatures, the bottles train the thermic sense in a controlled, repeatable way that builds the child's capacity to isolate and name sensory impressions. It's a straightforward work to present and maintain, and it fills an important gap in any complete sensorial shelf.