Stu, but remember the Roman Navy?
Stu, those Norsemans were good boats. Some of the Norsemans even invaded the Med. Weather the weight measurements using "stones" in England has anything to do with the weight of anchor stones is a good question.
There was this guy that came up with a newfangled solution to make the Roman Galleys faster by eliminating all that heavy weight on the bow. He discovered a new light-weight rock on Sicily made of cinder that size-for-size was much lighter than the old heavy rocks the Roman Navy was using. If I recall, I think his name was Fortrustus. Anyway, he found these light-weight cinder rocks then got a Galley to test them and somehow wound up with a glowing report.
The advantage to using a lightweight anchor rock is readily apparent because this meant the Galley could be a little faster. The Roman Navy subsequently bought up on this new technology and converted their ships.
To hopefully answer Pauls question, as for drums and whips, it was just about this time that Lions came into common use (you know, the Christians vs. the Lions?), and it was found the slave Oarsmen (or, now more politically correct, Oars-persons) could be threatened with the Lions instead of having to use whips. The advantage to this method meant there was now no need to have a Whipperson on board and this resulted in a further saving weight. As you know, those guys were big bruisers, and, it was a very tiring job.
As they say, "all is not gold that glitters" and the Romans soon found out that the new lightweight anchor rocks had some drawbacks such as rusty leachate (from the cinder rocks) that stained their bulwarks. One advantage to the old heavy rocks were they could be found on the beach, free for the taking, thereby eliminating the middlepersons (finally getting this down pat) to drive up costs.
There is not much said about the Fortrustus anchor rocks anymore although there are still some around used for backup for for special occasions.
