I got my drivers license in Nov 1962.  I was 18.

Wheat was handled in 3 bu bags off a Robinson's "Big E" harvester.  And if you can't remember, 3 bu of wheat weighs 180 lbs.

I loaded those 3 bu bags into a gravity bulk on a Chev Maple Leaf, using a 'bag to bulk' Mott loader. The open grain bag was placed on a loader, and a mechanical gear driven off the truck's PTO raised it up over the side, inverting it in the process and emptying the grain into the bulk. But each individual bag was shifted, using a bag hook in one hand, and ones knee to gain a bit of 'leverage' to swing the open bag maybe 6 or 8 ft to the loader.  When the 'swing' got to be too much to do in one movement, the truck was moved forward to get the loader close to the heap of bags once more, and the process continued.  When the grain started to return on the end of the loader shute, one had to climb up into the truck bin, and scrape the grain to the corners of the bin. [From memory - after about 60 bags].

The truck was nominally 5 ton capacity, but I loaded 100 by 180lb bags into it [yep 8 ton] and headed off to the grain receival silos on the rail tracks, 10 miles from the farm.

At the other end of the season -  cropping we call it in Aussy land - seed was in 150 lb 'butts', and single strength superphosphate was in 186 lb bags. Both were 'shouldered' off a truck tray, and carried to the seed drill, opened, and spread along the seed and fertilizer 'boxes'.

I did not question the 'wisdom' of performing such tasks, and had no back problems throughout my 54 yrs of grain growing farming.  Of course bulk handling of both harvested grain, and seed and fertilizer came in maybe 10 years afterwards, so before I was 30 yr old.

This is not skite-ing  - just telling you guys how it was!   40 or 60 lb bags!! Easy!

I reckon I could have still done both operations until I turned 70 - so 6 years ago.