At 43.5 weeks, I took one tablespoon of castor oil with some chocolate milk, went to bed. Ctx started at 3.30am, bowel action at 5am, ctx got strong enough that I couldn't sleep through by 6.30am. 3 cm dilated by 9am, 8cm by 2pm, baby out by 5.30pm. No meconium, no difficulties, BUT it was a comparatively small dose and I truly believe that it was the psychological act of saying "that's it, I'm ready for baby now" that tripped me into labour, because I didn't have any of the griping pains or diarrhoea other people talk about- I was begging for an enema when his head and membranes crowned
My second was an indirect castor oil induction- found the bottle, realised it expired at the end of the previous month, put it in the bin. Baby was born at lunchtime the next day, 2 weeks early but a much harder labour.
This time, I'm going to go and buy the castor oil the day I get to the point of totally fed-up, tie a "Drink Me" label on it like in Alice in Wonderland and put it somewhere obvious that I can meditate on it (like a high shelf where I see it every time I go past.)