VishhNu once brought 1000 lotuses and was placing them at your feet; after placing 999 flowers he found that one was missing; he plucked out one of his own eyes and offered it as a lotus; this supreme exemplification of devotion on his part was transformed into the wheel (sudarshana chakra) in his hand, which he uses for protecting the world .

हरिस्ते साहस्रं कमल बलिमाधाय पदयोः
यदेकोने तस्मिन्‌ निजमुदहरन्नेत्रकमलम्‌।
गतो भक्त्युद्रेकः परिणतिमसौ चक्रवपुषः
त्रयाणां रक्षायै त्रिपुरहर जागर्ति जगताम्‌॥ १९॥

VishhNu once brought 1000 lotuses and was placing them at your feet; after placing 999 flowers he found that one was missing; he plucked out one of his own eyes and offered it as a lotus; this supreme exemplification of devotion on his part was transformed into the wheel (sudarshana chakra) in his hand, which he uses for protecting the world .