Manava Dharmashastra 6.21

6.21

puṣpamūlaphalair vāpi kevalair vartayet sadā
kālapakvaiḥ svayaṃ śīrṇair vaikhānasamate sthitaḥ //

Or he may constantly subsist on flowers, roots, and fruit alone, which have been ripened by time and have fallen spontaneously, following the rule of the (Institutes) of Vikhanas.