‘In September 1956 IBM launched the 305 RAMAC, the first ‘SUPER’ computer with a hard disk drive (HDD). The HDD weighed over a ton and stored 5 MB of data.’

RAMAC itself stood for Random Access Method of Accounting & Control. The whole cabinet weighed over 1000kg and the 5MB data was spread over 50 huge aluminium disks, coated with magnetic iron oxide. The disks rotated at a speed of 1200rpm and the machines were leased for $3,200 per month back in the day.
This is how it looked like

Reference :
https://economictimes.indiatimes.com/slideshows/tech-life/12-weird-but-true-facts-about-technology/in-1956-5-megabytes-5mb-of-data-weighed-a-ton/slideshow/51419398.cms