Diaoyu Mountain (1259) — the same event in History of Yuan and Xu Zizhi Tongjian

History of Yuan: Xianzong died at Diaoyu Mountain, in the ninth year of his reign, aged fifty-two.; Xu Zizhi Tongjian: On the seventh month, day…

What each source says

History of Yuan (Yuanshi), Annals · AD 1259 · 釣魚山

Xianzong died at Diaoyu Mountain, in the ninth year of his reign, aged fifty-two.

癸亥,帝崩于釣魚山,壽五十有二,在位九年。
Location: 元史 卷3 憲宗 1259年 7月

Xu Zizhi Tongjian (Continuation of the Comprehensive Mirror) · AD 1259 · 釣魚山

On the seventh month, day guihai, the Mongol ruler (Möngke) died at Diaoyu Mountain at the age of 52.

秋,七月,癸亥,蒙古主殂於釣魚山,壽五十二
Location: 권175 七月 단락175.29.0

Place: 合州

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