釋氏稽古略 2.214

2.214

右元魏十二主一百四十九年分曰西東（西三王二十二年禪于周東一王十七年禪于北齊）。

The above concerns the Yuan Wei's twelve rulers across one hundred and forty-nine years, divided into West and East (in the West, three kings for twenty-two years, after which they abdicated to the Zhou; in the East, one king for seventeen years, after which they abdicated to the Northern Qi).