釋門歸敬儀 2.13

2.13

九曰肅拜者，但俯下手，今時揖者是也，亦指婦人拜。又肅或至三也，空首、奇拜唯一餘則再拜之。

The ninth is called the solemn bow (subai), merely lowering the hands, which is the bow of cupped hands (yi) in current times; it also refers to a woman's bow. Furthermore, su can sometimes be performed up to three times; the empty-head and single-knee bows are performed only once, while the rest are performed twice.