Miniscule
Usage notes
“The correct spelling is minuscule rather than miniscule. The latter is a common error, which has arisen by analogy with other words beginning with “miniâ€, where the meaning is similarly ‘very small’.†Oxford 1998
At the time of writing (22 May 2012), the number of hits in the printed works listed in Google Books for minuscule outnumbers those for miniscule by a large amount (by 1,990,000 to 422,000, a ratio of roughly 5:1). In contrast, the numbers of hits on Google (with language set to English) are 13,000,000 to 10,900,000, a ratio of about 6:5.