Hercules's Dog Discovers Purple Dye

It depicts the mythical discovery of Tyrian purple by Hercules and his dog, and was one of dozens of oil on panel sketches made by Rubens for the decoration of the Torre de la Parada in Spain.

A completed painting based on Rubens's sketch was made by Theodoor van Thulden in 1636–1638, and is now held by the Prado Museum.

[1] The painting shows a scene from an origin myth in the Onomasticon (a collection of names, similar to a thesaurus) of Julius Pollux, a 2nd-century Graeco-Roman sophist.

In Pollux's story, Hercules and his dog were walking on the beach on their way to court a nymph named Tyros.

[3] An oil painting based on Rubens's sketch by Theodoor van Thulden is in the Prado Museum.