Lexicons, Nirukta & Buddhist · c. 6th century CE
मन्दाकिनी वियद्गङ्गा स्वर्णदी सुरदीर्घिका ॥ १.१.११६ ॥
'The river of heaven.' Footnote: 'The Ganges of the sky, suggested probably by the milky-way.' — H.T. Colebrooke (1808)
'Ganges of the firmament' (viyat). Second synonym in the same verse. Note the form is viyad-, not the vyoma- that secondary literature often reports.
Amarakośa 1.1.116 (Svarga-varga) · text · translation