Manusmriti

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हिमवद्विन्ध्ययोर्मध्यं यत् प्राग् विनशनादपि । प्रत्यगेव प्रयागाच्च मध्यदेशः प्रकीर्तितः ॥ २१ ॥

sanskrit

That (country) which (lies) between the Himavat and the Vindhya (mountains) to the east of Prayaga and to the west of Vinasana (the place where the river Sarasvati disappears) is called Madhyadesa (the central region).

english translation

himavadvindhyayormadhyaM yat prAg vinazanAdapi | pratyageva prayAgAcca madhyadezaH prakIrtitaH || 21 ||

hk transliteration by Sanscript