Only this:
فریدونِ فرخ فرشته نبود
ز مُشک و ز عنبر سرشته نبود
(فردوسی)
One might expect the line of verse to read ز مشک و ز عنبر نسرشته بود.
It seems the negative verb disintegrates under the weight of its own form, so that سرشته becomes an attribute and stands independently of the verb, which in turn changes tense.