Sarvasiddhāntarāja (1639) · 1639 CE
No published e-text exists; the verse is readable in Pai & Shylaja's edition (JApA 42:113, 2021, open access), whose PDF is not machine-extractable (no ToUnicode maps). Pending an OCR proofread — never retyped.
Mānuṣaśīrṣa, the human head, with its coordinates as stated. — Literal rendering by the compiler
Ra's al-Ghūl, the Demon's Head, translated into Sanskrit; the Yantrarāja tradition's Pretaśira ('corpse-head') is the same image a generation earlier. The famous variable enters the Sanskrit record under a severed head's name in both. Identification and verse number per Pai & Shylaja (2021), Table 1; rendering after the edition's construal.
Sarvasiddhāntarāja, saṃkrāntyādi 11 (ed. Pai & Shylaja 2021) · text · translation