रात्रिभागौ द्वौ स्वप्नकाला त्रिभागः संवेशनोत्थानिकः ॥ कZ_०२.३१.०७ ॥
rātribhāgau dvau svapna-kālā tribhāgaḥ saṃveśana-utthānikaḥ
Deux divisions de la nuit sont consacrées au sommeil ; la troisième sert à se mettre au repos et à se réveiller (gestion/vigilance nocturne).
It implies planned night supervision—checks, repositioning, readiness to respond to disturbances—rather than leaving valuable assets unattended.