Skandapurana 14.34.4

14.34.4

tato yugasahasrāṃte vibuddhaḥ kamalāsanaḥ ..
ekākī ciṃtayāmāsa kathaṃ sṛṣṭirbhavediti .. 4 ..

then, at the end of a thousand yugas, the lotus-seated [Brahmā] awoke. / Being alone, he pondered: “How may creation come to be?”