An initiative petition for a constitutional amendment should be filed if an individual intends to submit a proposed constitutional amendment to the voters for approval or rejection.
HOW TO ORIGINATE A CONSTITUTIONAL AMENDMENT PETITION
To originate an initiative petition for a constitutional amendment, at least ten qualified voters of the Commonwealth may draw up and sign an original petition on which they put forward the full text of the constitutional amendment they wish to have enacted.
Each of the ten original signers must obtain a certificate of voter registration from the board of registrars or election commission in the city or town in which they are a registered voter. Each certificate of voter registration must be signed by at least three members of the board of registrars or election commission. These voter registration certificates and the original petition then must be submitted to the Office of the Attorney General by the first Wednesday in August.
Read further requirements here: http://www.sec.state.ma.us/ele/eleguide/guideamend.htm
You can find Petitions filed and approved by the AG here: Approved Petitions