Cassia - is the inner bark of an Indian tree (Cinnamomum cassia), which differs from that which produces cinnamon in the shape of its leaves and some other particulars. It was probably in ancient times, as it is at present, by far less costly than cinnamon, and it may have been on this account that it was used in double quantity.
An hin - Probably about six pints. See Leviticus 19:36.

And of cassia five hundred shekels,.... Or two hundred and fifty ounces:
after the shekel of the sanctuary; according to the standard weight kept there. This "cassia" was not the "cassia solutiva", which is of a purgative nature, and now in use in physic, but the "cassia odorata", or the sweet smelling "cassia": which, Pancirollus (s) says, some take to be the nard, out of which a most sweet oil is pressed; and Servius (t) says, that cassia is an herb of a most sweet smell. Pliny (u) speaks of it along with cinnamon; and Galen says, when cinnamon was wanting, it was usual to put in its stead a double quantity of cassia (w); Leo Africanus speaks of trees in Africa bearing cassia, and which chiefly grew in Egypt (x):
and of oil olive an hin; containing twelve logs: according to Godwin (y), it was of our measure three quarts; but, as Bishop Cumberland has more exactly calculated it, it held a wine gallon, a quart, and a little more: this was the purest and best of oil, and most fit and proper to be a part of this holy anointing oil.
(s) Ut supra, (Rer. Memorab. sive Deperd. par. 1.) tit. 11. p. 30. (t) In Virgil. Bucol. Eclog. 2. (u) Ut supra, (Nat. Hist. l. 12.) c. 19. (w) Apud Dalechamp in Plin. ib. (x) Descriptio Africae, l. 9. p. 752. (y) Moses & Aaron, l. 6. c. 9.

cassia--from the same species of tree as the cinnamon--some think the outer bark of that tree. All these together would amount to one hundred twenty pounds, troy weight.
hin--a word of Egyptian origin, equal to ten pints. Being mixed with the olive oil--no doubt of the purest kind--this composition probably remained always in a liquid state, and the strictest prohibition issued against using it for any other purpose than anointing the tabernacle and its furniture.