Mayamatam 15.26

15.26

madhyapaṭṭaṃkalāśraṃ cecchrīvajrastambhamucyate
agrākāraṃ yugāśraṃ syāt tripaṭṭakṣepaṇānvitam

if the middle fillet has sixteen facets, it is called a Śrīvajra pillar. / It may be square in its upper form, furnished with three fillets and projecting mouldings;