Ramayana
तासां नास्ति विशेषो हि दर्शने लक्षणे ऽपि वा । ततो ऽहमेकाग्रमनास्ताः प्रजाः परिचिन्तयम् ॥ 7-30-22 ॥
"Among them there was no distinction whatever, neither in appearance nor in marks; therefore, with single-minded attention, I pondered over those creatures."
english translation