On August 15, 1663, dozens of peasants attending Assumption Mass on Lake Robozero in Vologda Province watched a silent spherical fireball roughly 40 meters across hover for ninety minutes, reappearing three times; the water below lit to a depth of nine meters and fish fled to shore.

The account survives as a formal letter from witness Ivan (Ivashko) Rzhevsky to the Kirillo-Belozersky Monastery authorities, published in 1842 in the Russian Archaeographic Commission's 'Akty istoricheskie' (Vol. IV, pp. 331–332). Scholar Yury Roszius located what he claimed was the original manuscript, photographed in Aura-Z magazine (1994). Eyewitnesses reported burns from thermal radiation and a rust-colored discoloration of the lake surface. No conventional explanation, meteorite, aurora, ball lightning, fits the sustained duration and repeated appearances.