“The rule which seems to cover best the words of this group reads: “In diphthongs, i before e except after c or when sounded like a as in ‘neighbor’ and ‘weigh.’ ” Notice the phrase “in diphthongs.” “In the same syllable” might be substituted for this phrase. Usually this rule is stated without the prefixing phrase. In this case five more exceptions to the rule must be added to the eleven already mentioned, a total of sixteen exceptions.”
“The value of this rule seems fully as doubtful as that of the third rule. One hundred and one, about 2.6 per cent, of the words in the spelling list are covered by it. Eleven words, about 0.3 per cent, in the list are exceptions. In other words, the number of exceptions is about i i per cent of the number of words covered by the rule.”
Wheat, Leonard B., “Four Spelling Rules.” Elementary School Journal, 32, 1932, pp. 697-706.