A small, beady-eyed sparrow on one side of a set of scales heavily outweighs the gold and pearls which a weeping woman – two tears glistening on her cheeks – places in the other. Clearly, in the real word, this couldn't happen: the bird would be much the lighter than the jewellery. But this picture does not seek to depict the real world – it’s an allegorical painting, and the artist invites us to decode the message behind the central image of the impossible scales.

Nearly 400 years after the painting was made we can never be sure of the accuracy of our interpretations, but it almost certainly implies that no matter how much gold and how many pearls the woman loads onto the scales, their value can never match that of the sparrow. A bird could be symbolic of many things, but here it mostly likely represents virtue and true love – qualities which may also be reflected by the image of the two embracing putti carved into the stone next to it.

Why, then, is the woman weeping? And why too is there an image of another putto – or perhaps Cupid – in the niche behind her? The position of his arms and declining head closely match hers, and he too appears anguished. As well as the jewels, her expensive clothes and the costly ostrich feather in her hair suggest a wealthy lifestyle, and the implication is that this has been gained through prostitution. It is a trade-off which she now regrets.

This painting also has jewel-like qualities. It is slightly smaller than a paperback novel and is painted on a copper plate, which allowed the artist to create an exceptionally fine, bright finish. This style of highly meticulous small-scale painting was a speciality of Schalcken, which he learned from his teacher, Gerrit Dou, in Leiden. Another painting of very similar size (now in the Rijksmuseum, Amsterdam) by Frans van Mieris the Elder, who was also taught by Dou, shows a woman releasing a sparrow from a box. It is an allegory of the loss of virginity and was once in the same collection as Schalcken’s. It is possible that Schalcken’s picture was intended as a companion painting to represent the woman’s grief at her loss.