There were apparently some idiosyncracies in how they measured distance in Anglo-Saxon (or technically here I suppose Anglo-Danish) England:
According to a charter of 1023, Cnut gave to the monks of Canterbury the harbour of Sandwich, "with all the landings and dues on either side of the river from Pepperness to Marfleet... extending as far as a small axe can be thrown from a ship onto the land, when the ship is afloat and the river is in full flood."
They also possessed "anything in the great sea beyond the harbour, as far as the sea at the utmost recedes, and the length of a man holding a pole in his hand, and stretching himself as far as he can reach into the sea."
I do hope the monks of Sandwich went around throwing axes off ships and leaning over the sea with poles in their hands to test the exactitude of these measures.
The Latin and Old English can be found here; here's the relevant parts:
7 ic ann þam ilikan menstre to ðare munece bigleoue ða hæuene on Sandwic 7 ealle ða lændinge 7 þa gehrihte of ðam ilkan wætere of ægder healue ðas streames age land seðe hit age . fram Pipernæsse to Mærcesfleote . swa þæt þonne hit bið full flod 7 þæt scip bið aflote swa feorr swa mæg an taperæx beon geworpen ut of ðam scipe up on þæt land þa gereflanges of Cristes circean underfon ða gerihte...
7 gif aht is in ðare micelre sæ wiðutan ðare hæuene swa micel swa seo sæ heo mæst wiðteohð 7 git anes mannes længe þe healt ænne spreot on his hand 7 strecð hine swa feor swa he mæg aræcen into ðare sæ.
Here's something and nothing: in this same charter, Cnut also confirmed the presentation of his own crown on the altar at Canterbury. The earliest version of the famous story about Cnut and the waves - in which he theatrically demonstrates his inability to control the tide - concludes with Cnut placing his crown on a crucifix. Maybe this charter's emphasis on the extent of man's dominion over the seas isn't so odd after all...