Shiva Purana
अक्षिपक्ष्मपरिक्षेपो निमेषः परिकल्पितः ॥ तादृशानां निमेषाणां काष्ठा दश च पञ्च च ॥ ३ ॥
The time taken for the winking of an eye is Nimeṣa. Fifteen such Nimeṣas constitute one Kāṣṭhā.
english translation
akSipakSmaparikSepo nimeSaH parikalpitaH ॥ tAdRzAnAM nimeSANAM kASThA daza ca paJca ca ॥ 3 ॥
hk transliteration by Sanscript