Another version, from Cumbria (I got this from a letter in the Guardian about 1980):

Yan, tyan, tethera. methera, pimp, sethera, lethera, othera, dothera, deek, yandeek, tyandeek, tetheradeek, metheradeek, bumfit, yanabumfit, tyanabumfit, tetherabumfit, metherabumfit, jiggit.

That was as high as it went, you notched a stick for every 20 sheep.

Those numbers are closer to modern Welsh than most of the other versions posted here.