Yáo Kuān 姚寬 (1105–1162; CBDB id 10758; zì Lìngwēi 令威, hào Xīxī 西溪), native of Shèngxiàn 嵊縣 (modern Shèngzhōu 嵊州 in Zhèjiāng). Son of Yáo Shùnmíng 姚舜明 (Shàoshèng 4 = 1097 jìnshì; later Hùbù shìláng 户部侍郎 and Huīyóugé dàizhì 徽猷閣待制 in the early Southern Sòng). Yáo Kuān entered office on his father’s privilege (bǔguān 補官) without examination and rose through fiscal posts to quánShàngshū hùbù yuánwài láng 權尚書户部員外郎 (acting Deputy Director of the Department of Revenue) and Shūmìyuàn biānxiūguān 樞密院編修官 (Compiler in the Bureau of Military Affairs).
Yáo Kuān was a polymath of unusual range — the Xīxī jí 西溪集 (his collected works) is reported by Yè Shì 葉適’s postface as having reached two hundred juan, only a small portion of which survives. His best-attested work is the KR3j0036 Xīxī cóngyǔ 西溪叢語, a two-juan philological bǐjì; he also wrote on mathematics (the lost Xīxī wángshù 西溪忘數), on the Tàixuán jīng 太玄經, and on calendrical astronomy. Yè Shì’s postface records what is now Yáo Kuān’s principal claim to historical visibility: when Hǎilíngwáng Wányán Liàng 完顏亮 of the Jīn launched his southward invasion (1161), Yáo Kuān calculated by the courses of Tàiyǐ 太乙 and Yínghuò 熒惑 (Mars) that the Jīn must fail; the prediction was vindicated by the Jīn defeat at Cǎishí 采石磯 under Yú Yǔnwén 虞允文.
Note on the catalog meta: the project metadata for KR3j0036 Xīxī cóngyǔ gives “date: 1097,” which is in fact Yáo Shùnmíng’s jìnshì year (i.e. the father’s, not the son’s), and is incompatible with Yáo Kuān’s birth in 1105. The catalog has confused the two. The Xīxī cóngyǔ is properly datable to Yáo Kuān’s mature career, ca. 1140–1162.