Where did this notion come from?
As I learned, and going back to Austin Spare seems the same message, burning the sigil is merely a convenient method of disposing of the sigil if it were written upon paper.
The charging and activation of the sigil is done by achieving a state of gnosis and so planting the sigil into the unconscious. The classic method is to achieve gnosis through excitation by masturbation. Other methods of excitation or trance that bring the mind to single focus are also used. The “death posture” is another common technique.
Whatever the technique, charging involves an act of spiritual/psychological exertion. That is the method as I’ve learned it.
As an aside, charging and activating are usually a single act. That is, a charged sigil normally is immediately active unless you setup the sigil to activate at a later time or by a specific trigger.
This idea of simply draw the sigil and then burn it seems like someone for some reason dropped the key step from the process. It feels like someone decided to hold back the achievement of gnosis as an initiatory secret.
So… am I off base here? From whence came the practice of only using fire alone to charge sigils?
Either that or someone dropped discussion of charging sigils out prudishness about masturbation?
A few years ago I tried to start teaching a course on chaos magick at my local occult shop. It did not go over well. I asked the owner why they thought I wasn’t attracting participants, and they flat out said, “no one wants to do the work. You should just do spells for money.” (I did not go that route.)
In answer to your question, applying Occum’s Razor says it gets left out because it’s the hard part. Few people actually want to do the work. They see magick as a way to get things the easy way.