Where I am, it is common to use a White lead as a switched (output from switch) return of Hot to the light fixture. Really, it IS supposed to be identified as NOT a Neutral line at that switch, but many don't. (Black tape is much preferred for that than paint, since some paint can damage the insulation.) And it is the BLACK traveling from the power source to the switch box that MUST be used for the Hot supply.
My house had Knob-and-Tube (60 Amp service) wiring in it when we moved in over 45 years ago, and I replaced it all. So I have experience with it. There were no multi-wire cables. In this house, each single wire was encased in a black semi-flexible material like an old rubber, and then wrapped outside by a woven fiber sheath impregnated with something like a tar. Thus all those wires were black, no matter what their function. ALL those wires were copper, because that wiring system was used before Aluminum ever came into use for electrical wiring. However, I recall one possible reason for confusion. Most of those wires appeared silvery on the surface at first glance because they apparently had been "tinned". They were NOT aluminum, though.
There were no Ground leads from the fuse panel out to branch circuits. For each circuit a pair of black wires was run out from separate entry holes in the fuse box to use points. Along the sides of wood joists they were supported about every 3 to 5 feet by a ceramic tower or "Knob" about 2" tall that was nailed into the joist - one wire per knob. Often the two wires for a circuit were positioned on facing surfaces of joists in the same bay space between joists. Where a wire had to be run across joists or through a wall of floor plate, a hole was drilled in the wood and then a ceramic Tube installed in it, and the single wire run through that. Thus the term Knob and Tube. For a circuit with several use points (e.g., device boxes for outlets) the pair of wires was run like a power bus. At each use point a pair of shorter wires was spliced onto the pair of main lines (splices covered by friction tape) and run into the device box. Of course, all outlets were non-polarized 2-slot ones - no Ground, and no differentiation of slot sizes to differentiate Hot and Neutral.
The power leads to the electric stove in the house were suitable for 60 Amp load as most stoves now are rated. But they did not come from their own fuses; they were simply fed from the Hot and Neutral buses on the fuse box, and relied on the main service fuses (60 Amp) to protect the stove lines.
In this house, the early installers has actually installed fuses in BOTH the Hot and Neutral lines on each circuit. Nobody would do that today. I doubt it was supposed to be done that way when the wiring first was installed here, and that "normal" Knob-and-Tube systems did not do that, but I do not know for sure. However, such a system MIGHT have been used before we all started using the Grounded Neutral system in current use throughout much of the western world.
My house had Knob-and-Tube (60 Amp service) wiring in it when we moved in over 45 years ago, and I replaced it all. So I have experience with it. There were no multi-wire cables. In this house, each single wire was encased in a black semi-flexible material like an old rubber, and then wrapped outside by a woven fiber sheath impregnated with something like a tar. Thus all those wires were black, no matter what their function. ALL those wires were copper, because that wiring system was used before Aluminum ever came into use for electrical wiring. However, I recall one possible reason for confusion. Most of those wires appeared silvery on the surface at first glance because they apparently had been "tinned". They were NOT aluminum, though.
There were no Ground leads from the fuse panel out to branch circuits. For each circuit a pair of black wires was run out from separate entry holes in the fuse box to use points. Along the sides of wood joists they were supported about every 3 to 5 feet by a ceramic tower or "Knob" about 2" tall that was nailed into the joist - one wire per knob. Often the two wires for a circuit were positioned on facing surfaces of joists in the same bay space between joists. Where a wire had to be run across joists or through a wall of floor plate, a hole was drilled in the wood and then a ceramic Tube installed in it, and the single wire run through that. Thus the term Knob and Tube. For a circuit with several use points (e.g., device boxes for outlets) the pair of wires was run like a power bus. At each use point a pair of shorter wires was spliced onto the pair of main lines (splices covered by friction tape) and run into the device box. Of course, all outlets were non-polarized 2-slot ones - no Ground, and no differentiation of slot sizes to differentiate Hot and Neutral.
The power leads to the electric stove in the house were suitable for 60 Amp load as most stoves now are rated. But they did not come from their own fuses; they were simply fed from the Hot and Neutral buses on the fuse box, and relied on the main service fuses (60 Amp) to protect the stove lines.
In this house, the early installers has actually installed fuses in BOTH the Hot and Neutral lines on each circuit. Nobody would do that today. I doubt it was supposed to be done that way when the wiring first was installed here, and that "normal" Knob-and-Tube systems did not do that, but I do not know for sure. However, such a system MIGHT have been used before we all started using the Grounded Neutral system in current use throughout much of the western world.