IN HIS GROUNDBREAKING ARTICLE ‘A Buddhist mantra recovered from the Ratu Boko plateau: A preliminary study of its implications for Śailendra-era Java’, Jeffrey Sundberg (2003) highlighted an important gold artefact recovered from the Ratu Boko hillock near Prambanan in Central Java. The artefact, an inscribed gold foil consisting of two connected diamond-shaped leaves recalling a vajra, bears the Sanskrit mantra oṁ ṭakī hūṁ jaḥ svāhā repeated on each of its four sides. A unique, and intriguing, feature of the inscription is the engraving of the words panarabvan and khanipas within an exaggerated circular bubble in the two cases of the grapheme ī in the sequence ṭakī. This feature led Sundberg to advance the hypothesis that the artefact, and the mantra(s) inscribed on it, was connected to King Rakai Panaraban (r. ad 784– 803), who is known to us through the inscription of Wanua Tengah III recovered from Central Java, as well as from the 16th-century Old Sundanese historical chronicle Carita Parahyaṇan(Sundberg 2011). Sundberg (2003) discovered instances of very similar mantras (i.e., TAKKI HŪṀ JAḤ, ṬAKKIJJAḤ HUṀ) in Sanskrit, Tibetan, and Sino-Japanese Tantric Buddhist texts, and pointed out that in the Sanskrit Sarvatathāgatatattvasaṇgraha(STTS)— a 7th-century mūlatantraconsolidated over time into the Yogatantra tradition (Weinberger 2003: 4)—the mantra occurs in the context of the Buddhist Trailokyavijaya myth or the ‘Subjugation of Maheśvara’ by the Bodhisattva Vajrapāṇi, while in Sino-Japanese sources it is associated with Aizen's subjugation of Īśvara and Nārāyaṇa. In view of these interesting facts, Sundberg concluded that the epigraphic document was Vajrayāna in nature, thus opening the grounds ‘to find expressions of these tantric convictions in the stone temples of Java’ (ibid.: 181); that it might have had an anti-Śaiva character (and purpose)—being a repudiation in strong terms of the religion of Panaraban's ancestor Sanjaya (ibid.: 183); and that it was devised by Panaraban, in order to ‘link himself to the mantra or the cosmic being it points to’ (ibid.). In the conclusion to his essay, Sundberg anticipated that the study of this mantra ‘has hopefully only just begun’ (ibid.), and invited scholars with the necessary philological skills to search for attestations of this mantra in textual sources from South, Central, Southeast, and East Asia…