A Javanese myth about a just and powerful leader of humble origins became a hot topic in Indonesian media this week when it was linked to the campaign of presidential candidate Prabowo Subianto. Images circulated online of banknotes stamped with the words 'Prabowo Satria Piningit Heru Cakra Ratu Adil' ('Prabowo: Hidden Knight, Era of the Just King').

In the prophesies of Javanese King Jayabaya, a hidden knight is predicted to one day rise to become the rightful king of the archipelago, and then the world. Many leaders in Indonesian history have claimed to fulfil the prophecy, from Gajah Mada of the Majapahit Empire to former presidents Sukarno and Suharto.

The stamped banknotes were suspected to be a campaign tool used by Prabowo's party Gerindra (the Greater Indonesia Movement) to associate him with the Javanese legend. They were also suspected to have been used as bribes, stamped with Prabowo's name to remind voters where the money came from.

Gerindra has denied responsibility for the stunt, calling it a 'black campaign' against Prabowo by suggesting he handed out bribes and engaged in campaigning outside the official campaign period scheduled for late June. It has also been suggested that the stamps were a grassroots initiative carried out by Prabowo's supporters without party approval.

The island of Java is the centre of power and wealth in Indonesia, and all of the country's presidents since independence have been Javanese (even Sulawesi-born president BJ Habibie had a Javanese mother).

Prabowo comes from an aristocratic Javanese family, and can hardly be said to be of humble origins – the former leader of the army's special forces (Kopassus) was once married to president Suharto's daughter, and his bid for president is reportedly backed by his billionaire brother, Hashim Djojohadikusomo.

Whether or not Prabowo can claim the title of the unknown knight who becomes a just king, his Javanese roots are likely to resonate with some voters in Java, where in rural areas belief in mystic traditions remains strong.

However, Java is also a place of modernity and home to some of the biggest Twitter-using cities on earth. The first known image of a stamped banknote was sent by Twitter user @simonperes, who says he received the notes as change while buying food on the Jagorawi toll road outside Jakarta (the photo above is taken from Peres' tweet).

Bank Indonesia, the central bank, has declared the stamped banknotes to be unsuitable for use as legal tender and has offered to exchange them for clean cash.

Whether or not Gerindra is responsible for the stamped notes, it seems that in this year's net-connected presidential election, there are some old tactics that the public just won't buy.