As I understand it, the human work probably wasn't directly taxed. I'm guessing that what was taxed as the incomes of the humans. This may seem like a meaningless distinction, but the humans have other opportunities to earn taxable incomes.
All that said, you seem to be getting at the notion of a Universal Basic Income. It's an increasingly popular idea in some political circles.
I think the point Kalium was trying to make is that it's not possible to quantify the value of human labor without pinning it to the income someone earns from doing it. A programmer's job is less physically labor intensive then a farm worker's, who obviously earns less. And there are numerous skills and fields more complex then programming that nobody will pay as much, or at all, for someone to do.
For a machine, it's value is directly tied to the profits gained by it's operation relative to it's operating costs, which is the business income that is already taxed. I think the taxing of machine "work" jeena was asking for would basically just be an increase in taxes on corporate profits, perhaps with some variation based on how many people they employ relative to their profits.
(Google Translate calls it 'gainful employment', no idea if it's the right translation. What I mean is work for which you're getting paid money which you need to use to survive.)