DS was actually 21 weeks. That's pretty much suicide to admit on MN
He was BLW. He was sitting (with support - he didn't sit alone until 9 months old) and he was literally going insane every time I ate something and was clawing his way up me trying to grab it. This sounds astonishing but I have diary entries of the time, which prove I'm not misremembering the time frame. He was a baby who was just very determined to move and he did a lot of pulling himself around before he was actually mobile. He absolutely got the food to his mouth himself, I never ever put items of food in his hand or hold them to his mouth. I did not spoon feed until well after 6 months. It was the height of the BLW "craze" - I even bought the book! And so I stuck to the theory to the letter. Which, BTW, says that you can do BLW "from birth" because if you put a boiled carrot in front of a newborn, clearly they don't have the capacity to eat it, in the sense that they don't even have the physical capability to get it to their mouths. So the theory doesn't specify an age for starting, it just recommends that you follow guidelines set by research, which is no earlier than 17 weeks and as close to 26 as possible. But his first food was buttered toast. So I did introduce gluten before 6 months, which is supposed to be a no-no. However, one theory says that if their external development is there in terms of sitting with support, being able to get things to their own mouth and swallow, (which initially, they don't always do) then it follows that it's likely the internal development is in line, because it doesn't make much sense otherwise. I realise that something sounding logical isn't the same as it being true, but in the absence of evidence either way, the face of the vehementness of this baby, the fact he was over 17 weeks and the fact that millions of other parents wean early for much more spurious reasons led me to go for it.
I really liked Analytical Armadillo's article about the biggest myths surrounding weaning. It mirrored my thoughts and it's backed up (where possible) by research which is nice. It came long after I'd done the weaning thing but is was nice to read anyway!
www.analyticalarmadillo.co.uk/2013/09/13-baby-led-weaning-myths.html
I know that people say "Oh they watch you drive, and use knives and you don't let them do those things!" but there is a difference between a baby passively watching you with interest - which most of them do, most of the time, and yes, they have absolutely no comprehension that you putting things in your mouth equates to eating, tasting, or satiating hunger. Why would they know that? They've never done it. But when they are actively exploring food by reaching out for it, holding it, licking it, smelling it, it seems silly - you let them explore all kinds of things when they are in that stage, it seems ridiculous to totally avoid all food as though it might be some kind of poison. You can let them have a bit to explore when they are interested and leave it when they are not, it's not like as soon as you start you're on a train to 3 meals a day and you can't get off it.
The one thing which is really important is that you must ensure they are sitting upright and not slouched backwards. If they can't sit for the duration of a meal then it's not a good idea to start because of choking hazards. Also if you're putting items in their mouth or hands, you're introducing items which they can't naturally pick up which might mean that you're introducing choking hazards. An example was given of the pincer grip development - it would be a spectacularly bad idea to feed a 6 month old a spoonful of sweetcorn kernels or peas, but to let a 9 or 10 month old pick up individual peas or bits of sweetcorn is okay because they are controlling it themselves.
(Bonus: While I was looking for the AA article I found this which I also liked. It repeats a number of points but might add more info on some others.)
www.analyticalarmadillo.co.uk/2011/02/starting-solids-can-babies-be-ready.html