The second recipe given here seems almost relevant. And if I didn't know better I'd say this was coming straight out some form of "high academia".
https://www.thevespiary.org/rhodium/Rhodium/chemistry/meth.hi-p.html
PROCEDURE 2
In a 500 mls round-bottom flask is added 150 mls of glacial acetic acid, 15 grams of red phosphorus, and 33.50 grams of iodine.
[NOTE 6] The mixture is allowed to react for 15 - 20 minutes, until all of the iodine has reacted. Then add 10 mls of distilled water and mix, then add 8.07 grams (0.04 mole) of EPHEDRINE HCl, and mix. A reflux condenser is added to the 500 mls round-bottom flask and the mixture is gently refluxed (gently boiled continuously) for 2 and 1/2 hours. The hot mixture is suction filtered while still hot to remove the excess red phosphorus.[NOTE 7] The hot filtrate is added slowly by pouring into a solution of 20 grams of sodium bisulphite in 1 liter of distilled water. The solution is made basic and solvent extracted as above using two 100 ml portions of ether, washed and dry.The oily residue extracted (after removing the ether) is a mixture of methamphetamine, iodo-ephedrine and minor amount of acetic ester ephedrine.[NOTE 5]
[NOTE 6] Alternatively, 150 mls of hot distilled water, 15 grams (0.48 moles) of red phosphorus, and 33.50 grams (0.132 moles) of iodine in small 3-5 gram portions is added. The mixture is allowed to react for 15-20 min, until all of the iodine has reacted. Then add 8.07 g (0.04 mole) of EPHEDRINE HCl and follow Procedure 1. The yield is 80-88%
[NOTE 7] Have some hot glacial acetic acid on hand to rinse the flask and the filtered red phosphorus.
Calculation of HI to Ephedrine Ratio
In Procedure 1 and 2, two moles of HI react with one mole of Ephedrine giving Methamphamine and I2.
Ephedrine + 2HI ==>> Methamphetamine + I2 + H2O
Therefore the Ephedrine:HI ratio is theoretically 1:2, but to assure that the reaction goes to completion, the actual ratios used above are 1:3.3
This ratios has been calculated as follows:
Procedure 1:
1 ml of 57% HI = 0.99 grams of HI
170 mls of 57% HI = (170 x 0.99) = 168.3 grams of HI = 1.32 moles HI
Since we use 0.4 moles of Eph then (1.32/0.4) = 3.3
Since the reaction of phosphorus, iodine and water is 2 P + 3 I2 + 6 H2O --> 6 HI + 2 H3PO3 the ratio of HI:I2 is 3:3
Procedure 2
For every 0.04 moles of Eph, then (0.04 x 3.3) = 0.132 moles of HI, since the ratio of HI:I2 is 3 : 3 = 1, then we need 0.132 moles of I2 = 33.50 grams of I2.