My 17th Century Dutch isn't so good but I can still look at the illustrations in Johan Picardt's 1660 book "Korte beschyvinge van eenige vergetene en verborgene Antiquiteten" eg here, here and here. Mr Picardt is considered the founding father of the study of archaeology in the Netherlands. The drawings seem to show the hunebedden being built by giants and dwarfs. But the dwarfs seem to get the raw end of the deal as the giants end up eating them. That's certainly what it looks like at any rate.
Throughout Europe and even adjacent areas there was the widespread belief in thunderstones. These peculiar stones (prehistoric flint and stone axes) were thought to have crashed into the earth during a lightning strike. Although nowadays this superstition has largely vanished, it was still widely accepted in the first half of the 20th century.
Deinse* describes this situation for the Dutch province of Overijssel, directly south of Drenthe. He reports that virtually every farmer has at least one prehistoric axe at his farm. They were believed to protect the house against lightning, as lightning never strikes the same place twice. He even reported that particular axes were believed to possess special powers. Small bits of stone were scraped off these axes and were given to children as a medicine against convulsions.
Deinse, J.J. (1925): Uit het Land van Katoen en Heide - Oudheidkundige en Folkloristische schetsen uit Twente. p102-111
This is from p25 of 'Ceci n'est pas une hache. Neolithic Depositions in the Northern Netherlands' by Karsten Wentink, 2006 - which you can read online at Google Books - it has lots of Serious archaeological information and discussion in it.
Grafheuvel No 13 in the Westerheide is one of the most attractive of all. It's also the one the casual visitor is most likely to miss as it stands in a sheltered tree-lined glade just off the main heathland. Although not actually hard to find (if you are looking for it), it cannot be seen from the main path that follows the tree-line. It lies almost equidistant between Grave Mounds 9 and 7.
This barrow is a symmetrical grassy dome, rising to about 2 metres, and with a spread of approximately 15 metres.
Grave Mound 12 on the Westerheide has, despite a probable height of two metres, an extremely low profile as it rises very gradually. This is the most extensive mound in the heathland, with a width that I estimated to be at least 30 metres.
Grafheuvel No 11 in the Westerheide is small and inconspicuous. Completely heather covered, it could well be mistaken for a mere undulation in the heathland, rising to about 2 metres and around 10 metres wide.
Westerheide 10 is the most easterly of the grave mounds in this area, and is found on the edge of woodland, 300 metres along the main path north through the reserve and approximately 50 metres to the left.
This is a low, grassy mound, struggling to attain a height of one metre, and rather less than ten metres in width.