Śaiśirīya Śikṣā 7

7

yādayaśca smṛtā hyaṣṭau catvārastu yamāḥ smṛtāḥ
anusvāro visargaśca ḷakāraśca tathaiva ca

and eight are taught beginning with ya, and four are taught as yamas; / the anusvāra, the visarga, and also the sound ḷ,