While Mr Jongejans conceded that Mangamuka Summit might not be 4383m above sea level, the sign did not specify the base point from which the height was measured so it could in fact be correct.
He hoped the sign would remain as it is, saying it gave people something to ponder and challenged old ways of thinking.
Further enquiries reveal the true height is closer to 383m than 4383m. A Kiwimaps booklet found under a pile of chip wrappers and council agendas in an Advocate vehicle gives a height of 395m for Mangamuka Summit, while a topographic map published by NZ Topo Maps puts the elevation at 380m.
The nearby, and higher, peaks of Maungataniwha and Raetea are 572m and 744m, respectively.
The figure on the sign appears professionally applied and there is no obvious sign of tampering.
One possibility is that an error occurred in the NZ Transport Agency's sign-making workshop, or that one of its employees is a proud Northlander with a sense of humour.
Another is that a local has sourced a number "4" of just the right size and font and carefully added it to the sign.
In the meantime we advise anyone keen to scale a 4000m peak, but who doesn't like snow, heights or oxygen deprivation, to head to Mangamuka Summit before the sign is corrected.