Lǐ Dàn 李旦 (662–716), posthumously titled Emperor Ruìzōng 睿宗 of Táng. Fourth son of Emperor Gāozōng 高宗 and Wǔ Zétiān 武則天; reigned briefly 684–690 as his mother’s puppet before her formal usurpation, and again 710–712 after the coup against Wéi 韋后, until his abdication in favour of his son Xuánzōng 玄宗 (Lǐ Lóngjī 李隆基). As Tài-shàng-huáng 太上皇 (Retired Emperor) he composed the celebrated imperial preface to 菩提流志 Bodhiruci’s 120-fascicle Mahāratnakūṭa compilation, completed in Xiāntiān 先天 2 (713).