Theophilus Thistledown, the successful thistle sifter, in sifting a sieve full of unsifted thistles, thrust three thousand thistles through the thick of his thumb. See that thou, in sifting a sieve full of unsifted thistles, do not get any of the thistles stuck in thy tongue.

She sits by the seashore selling seashells.

If the party of the first part lease a great grater to the party of the second part, and the party of the second part lease a little grater to the party of the first part, then the party of the first part, being the lessor of the greater grater and the lessee of the lesser grater, shall be deemed the greater lessor and the lesser lessee, whereas the party of the second part, being the lessor of the lesser grater and the lessee of the greater grater, shall be deemed the lesser lessor and the greater lessee.

Sixty-six sick chicks.

The seething sea ceaseth and thus the seething sea sufficeth us.

(According to William Poundstone, this last one is by far the hardest. In his sample, only 3% got it right the first time.)