I have been having issues trying to explain to new hikers coming with me to the Berg the importance of making a backpack as light as possible, apparently they don't catch the difference that the 200 gram book they are currently reading makes over a 2 or 3 day hike (they also don't seem to realise that they will be so tired that they will not want to read it, or the fact that they may alert locals to our possition by reading it at night). After discovering that 3 guys in a group of 4 (me being the 4th) had brought custard and a full packet of melie meal on a 2 day hike up Langalibalele Pass, and then persisted to complain about how heavy their packs were (and insist that the tent which we will all sleep in is entirely my problem to carry), I have come up with a new device to illustrate the actual effects of 200 grams on a backpack. I call it the tons per hour ratio.
The assumption is that a fairly slow hiker will walk just over 3 kms in 1 hour, taking about 3 steps per metre and therefore say 10 000 steps per hour. Every gram in a pack is lifted and dropped by each footstep taken and therefore every gram carried needs to be multiplied by 10 000 to get its weight per hour. On this assumption, a 200 gram book will add 2 tons per hour to a backpack (that is a scary thought!). So basically carrying that book in a backpack on a day when 12km of hiking happens is the same amount of work as taking 4 hours to move a 1 ton car 2 footsteps from where you started, by actually picking it up and moving it! And thats before you take into account the fact that your backpack itself probably weighs about 2.5kgs!
I plan to test this explanation next time I plan a hike, this after having just failed to climb Popple Peak on my 3rd attempt this year after having a group of 2 people and the other guy not being nearly as fit as I thought (the plan having been go from Giant's Castle camp to Judge pass, camp there on night 1, climb the pass on day 2, climb Popple and the Judge, come down Corner pass, camp at the base and walk back to the car park on day 3, it ended up being hike to Bannerman Hut, climb the Bannerman Pass on day 2, turn around at the top due to taking too long to get up the pass (4h30 to climb a 3km pass is not acceptable, neither is the 5h to get back down!) and spend night 2 back in the hut, fortunately we said in the mountain register that we may use Bannerman Pass in an emergency, so they might have looked for us there if something went wrong)...
. @ghaznavid...your "tons per hour" device is a gem!! 
