Complex sentence: His name is connected with the humane treatment of the insane, for whose care he projected in 1792 The Retreat at York, which became famous as an institution in which a bold attempt was made to manage lunatics without the excessive restraints then regarded as essential.
Split into simpler sentences: His name is connected with the humane treatment of the insane, for whose care he projected in 1792 The Retreat at York. This place became famous as an institution in which a bold attempt was made to manage people in mental distress without the excessive restraints then regarded as essential.