IshGen 35:5 :ܠܡܢܬܐ ܡܨܥܝܬܐ ܘܬܛܝܪܬܐ ܩܒܥܗ݀ ܒܐܣܦܝܪ ܣܗܪܐ‏ : He set the middle one, the one with left overs (of bright purity) in the moon's sphere
See the entire entry for taṭṭīr adj. impure