大毘盧遮那成佛經疏 10.75

10.75

次一切佛頂者，一切佛頂謂十佛剎土微塵數佛之頂，頂是尊勝之義，最在身上也。即是十八佛不共法之別名。此本尊形像，一同釋迦具足大人之相，唯頂內髻作菩薩髻形為異也。亦住寶處三昧而說此真言。

Next, 'all uṣṇīṣas' refers to the uṣṇīṣas of the buddhas as numerous as the dust motes of ten buddha-kṣetras. 'Uṣṇīṣa' has the meaning of noble supremacy, situated topmost upon the body. It is another name for the eighteen distinct qualities (āveṇikadharma) of a buddha. The form and appearance of this principal deity is entirely identical to Śākyamuni, fully possessing the marks of a great person, differing only in that the topknot within the uṣṇīṣa is shaped like a bodhisattva's topknot. It also abides in the Ratnasambhava samādhi and speaks this mantra.