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On June 24 (or possibly June 18) in 1178, five Canterbury monks report something exploding on the moon.  This passage appears in the medieval chronicles of Gervase of Canterbury.

About an hour after sunset on June 18, 1178 A.D., a band of five eyewitnesses watched as the upper horn of the bright, new crescent Moon "suddenly split in two. From the midpoint of this division a flaming torch sprang up, spewing out . . . fire, hot coals and sparks. . .The body of the moon, which was below writhed. . .throbbed like a wounded snake."

A geologist suggested in 1976 that this account is consistent with the location and age of the 22-kilometer (14-mile) lunar crater Giordano Bruno, the youngest crater of its size or larger on the Moon.  If this hypothesis is correct, it would be the only recorded time an asteroidal impact has been observed with the naked eye.

Based on the size of the crater, it must have been a one-to-three kilometer wide (a half-mile to almost 2-mile wide) asteroid that blasted Giordano Bruno into the Moon's northeast limb.

Paul Withers of the University of Arizona Lunar and Planetary Laboratory suggested in the April, 2001 issue of Meteoritics and Planetary Science that such an impact would have triggered a blizzard-like, week-long meteor storm on Earth -- yet there are no accounts of such a storm in any known historical record, including the European, Chinese, Arabic, Japanese and Korean astronomical archives. . 

Withers believes those five ancient sky-watchers might have seen the fiery display of a meteor traveling along their line of sight rather than an impact on the moon.

"I think they happened to be at the right place at the right time to look up in the sky and see a meteor that was directly in front of the moon, coming straight towards them."

Primary Source:  https://science.nasa.gov/science-news/science-at-nasa/2001/ast26apr_1/