Bhagavatapurana 8.2.2

8.2.2

tāvatā vistṛtaḥ paryak tribhiḥ śṛṅgaiḥ payonidhim /
diśaḥ khaṃ rocayannāste raupyāyasahiraṇmayaiḥ //

2. It occupies an area of as many yojanas as it is high, and it has three summits of gold, silver and iron with which it illuminates the sea of milk, the cardinal points and the sky;