Tantra Sāra 1.028
शङ्खचक्रगदापद्मधराश्चैते हि सर्वशः। क्रमव्युत्क्रमपद्मादि गदादिव्युत्क्रमस्तथा। अर्धक्रमः सान्तरश्च षट्सु षट्स्वरिपूर्विणाम् ॥२८॥
They are all (24 forms) carrying conches, discs, clubs, and lotuses always. They are holding lotus in order and then in reverse order, then the club in reverse order, then in half order, then in intervals, grouped in six of the six preceding six vowels.
Note:
A pictorial representation of 24 forms is the order described:
