Manusmriti
अस्थिमतां तु सत्त्वानां सहस्रस्य प्रमापणे । पूर्णे चानस्यनस्थ्नां तु शूद्रहत्याव्रतं चरेत् ॥ १४० ॥
But for destroying one thousand (small) animals that have bones, or a whole cart-load of boneless (animals), he shall perform the penance (prescribed) for the murder of a Sudra.
english translation
asthimatAM tu sattvAnAM sahasrasya pramApaNe । pUrNe cAnasyanasthnAM tu zUdrahatyAvrataM caret ॥ 140 ॥
hk transliteration by Sanscript