(Chapter 19, Verse 1) Thus says the Lord: Go, and take the potter's earthen bottle, and take of the ancients of the people, and of the ancients of the priests. For the potter's bottle, which is called 'Bocboc' in Hebrew, the Septuagint translated it as 'doliolum'. But divine Scripture wants to instruct the people not only with their ears, but also with their eyes. For what is seen is more retained in the mind than what is heard: 'Take,' he says, 'your little bottle or earthenware jar as a witness.'
Source: Commentary on Jeremiah