Manasara 50.89

50.89

madhye cāgraviśāle tu tattadaṃśena hīnakam
āmadhyāgraṃ kṣayaṃ kuryādagrayorbalayānvitam

In the middle and at the tip width, it is reduced by corresponding parts; / one should make a tapering from the middle to the ends, furnished with a ring at both ends.